{
  "id": "measles",
  "title": "Measles",
  "lang": "en",
  "source_lang": "en",
  "summary": "A highly contagious viral disease caused by measles virus, covering its biology, clinical course, vaccination, global elimination efforts, and current resurgence.",
  "category": "health",
  "subcategory": "diseases",
  "type": "concept",
  "aliases": [
    "Rubeola",
    "Morbilli",
    "麻疹"
  ],
  "generated_at": "2026-10-09",
  "model": "pro/claude-haiku-5-5",
  "url": "https://aiwiki.page/en/measles/",
  "translations": {
    "zh-Hans": {
      "url": "https://aiwiki.page/zh/measles/",
      "json": "https://aiwiki.page/zh/measles.json"
    }
  },
  "sections": [
    {
      "heading": "",
      "text": "Measles is an acute, highly contagious infection caused by the measles virus, a single-stranded RNA virus in the genus Morbillivirus and the family Paramyxoviridae. It infects only humans, spreads mainly through the respiratory route, and produces fever, cough, runny nose, conjunctivitis, and a characteristic rash. It is among the most transmissible of all human infectious diseases, and its viral biology explains both its ease of spread and the severity of its complications.\n\nFor most of recorded history, measles was a leading cause of illness and death in young children, and its outbreaks shaped the health of cities and of populations exposed for the first time after contact with others. Since the first licensed vaccine in 1963, global mortality has fallen sharply, and the disease has been a central case in public health and immunology. One of its distinctive features is that infection can suppress immune memory, leaving survivors more vulnerable to other infections for an extended period.\n\nThis entry covers the virus and its structure, transmission and clinical course, complications and high-risk groups, diagnosis and treatment, the immunology of infection, the discovery and development of vaccines, historical epidemics, global control and the criteria for elimination, the 2025–2026 resurgence in the Americas, the role of vaccination coverage in outbreaks, outbreak response, socioeconomic impacts, related viruses, and open research questions."
    },
    {
      "heading": "Virus structure and genome",
      "text": "Measles virus belongs to the genus Morbillivirus in the family Paramyxoviridae. Its genetic material is a single strand of RNA that is not divided into segments and has negative polarity, meaning the genome must be copied into a complementary strand before the virus can be expressed. The genome is about 16 kilobases long, and it encodes six structural proteins: nucleoprotein (N), phosphoprotein (P), matrix (M), fusion (F), hemagglutinin (H) and the large (L) protein. N, P and L form the core complex that carries out replication and transcription, and the M protein lies beneath the envelope and surrounds this complex.\n\nThe virion is enveloped in a host-derived lipid membrane that carries two glycoproteins, H and F. H binds to cellular receptors, while F drives the merging of the viral and host membranes. The two proteins act together, and F depends on H for its activity during entry. Structural studies show that the top of the H head is partly masked by N-linked sugars, forming a glycan shield that limits antibody access to the receptor-binding site. The lipid envelope is also the reason the virus survives poorly outside the body: it is inactivated by heat, ultraviolet light and drying, which is why transmission depends on close contact and on airborne droplets.\n\nReceptors and sites of replication\n\nWild-type clinical isolates enter cells through two receptors: signaling lymphocytic activation molecule (SLAM, also known as CD150) and nectin-4, also called poliovirus receptor-like 4 (PVRL4). Vaccine strains can additionally use CD46, a complement regulator. SLAM is expressed on B and T lymphocytes, immature thymocytes, monocytes and dendritic cells, and the macrophages found in the respiratory tract. Infection usually begins in these immune cells in the lung or upper airway. Infected lymphocytes then carry the virus to nearby lymph nodes and spread it to lymphoid tissue throughout the body.\n\nNectin-4 is expressed on epithelial tissue, including the alveolar epithelial cells of the lung. Because the virus can replicate in these cells and reach the airway surface, this route is considered central to shedding and onward transmission, while SLAM-dependent infection of immune cells drives the immunosuppression that follows. In this sense, receptor usage explains both where the virus multiplies and why it can damage the immune system.\n\nGenetic stability and antigenic uniformity\n\nThe RNA-dependent polymerase of measles virus has a relatively high mutation rate, and laboratory experiments can select escape mutants that evade individual neutralizing antibodies. Despite this, the virus has remained monotypic, meaning that all known strains share a single serotype. Genetic diversity is tracked as genotypes based on nucleotide sequence, but these lineages do not differ enough in antigenic structure to require separate vaccines. Studies of vaccine-induced antibodies have found that protection from a vaccine derived from a single lineage still neutralizes currently circulating genotypes. This antigenic uniformity is the main reason one vaccine formulation can be used across different populations and regions, and it is also why the vaccine design does not need to be updated in the way seasonal influenza vaccines are.\n\nRelationship to genome analysis\n\nBecause the genome is small and its sequence changes slowly at the level of antigens, sequence data are useful for tracing transmission chains, even though they do not alter the serotype. The genome and its encoded proteins therefore form the basis for both epidemiological tracking and vaccine design, and the H and F glycoproteins remain the principal targets of protective immunity."
    },
    {
      "heading": "Transmission and routes of spread",
      "text": "Measles spreads mainly through respiratory secretions. When an infected person coughs, sneezes, or talks, the virus leaves in droplets that other people can inhale or that can land on the eyes, nose, or mouth. Transmission happens person-to-person among close contacts, and the virus can also reach a new host indirectly, when someone touches a contaminated object and then touches the face. Handling or touching contaminated objects and then touching your eyes, nose, and/or mouth is one such route.\n\nBeyond short-range droplets, the virus also travels on fine airborne particles that stay suspended in the air. These particles can remain in a closed area for up to 2 hours after the person with measles has left. A 2014 investigation of two travelers who had passed through the same gate at a Chicago airport illustrates this. Transmission most likely occurred in the gate area during a 46-minute interval between the arrival of the adult's flight and the scheduled departure of the child's flight. Genotyping showed that both cases were genotyped as D8, and the corresponding nucleotide sequences were determined to be identical.\n\nThe period of greatest infectiousness comes before the rash. Maximum communicability occurs from onset of prodrome (or first symptoms) through the first 3-4 days of rash. Sources differ on the exact window: the CDC gives 4 days before through 4 days after the rash appears, while ECDC describes people as contagious from about five days before the onset of rash to four days afterwards. Because the early phase resembles an ordinary respiratory infection, an infected person can spread measles to others even before knowing they have the disease, which is why cases are frequently identified only after exposures have already occurred.\n\nHumans are the natural hosts of measles virus, and no animal reservoirs are known to exist. The virus therefore cannot persist in wildlife or livestock between human outbreaks. Its continued circulation in a given area depends on a steady supply of susceptible people, such as young children and unvaccinated adults. When immunity in a population is high enough that new cases stop arising, a chain of transmission breaks, and the virus disappears locally until it is reintroduced from elsewhere.\n\nThe transmissibility of measles is usually described by the basic reproduction number (R₀), which is the average number of secondary cases produced by one case in a fully susceptible population. For measles, R0 is often cited to be 12–18, which means that each person with measles would, on average, infect 12–18 other people in a totally susceptible population. Among the common vaccine-preventable diseases, this value is generally recognised as one of the highest. The same R₀ value sets the threshold for herd immunity. Using the relation \\(p = 1 - \\frac{1}{R_0}\\), where \\(p\\) is the immune fraction needed to stop sustained spread, gives about 92% for R₀ = 12 and about 94% for R₀ = 18. This is why measles is treated as a benchmark for the level of population immunity required to stop transmission.\n\nThese figures are theoretical. R₀ assumes that nobody in the population is immune, and when considering diseases with pre-existing levels of immunity (e.g. childhood diseases like measles), R0 is a theoretical value representing what could happen in terms of disease transmissibility by removing immunity. In these cases, an appropriate measure of diseases transmissibility is provided by the effective reproduction number. A systematic review also found that R0 estimates vary more than the often cited range of 12–18. In practice, the transmission risk for any given setting depends on the local immunity profile, and the measured value can differ from the textbook range."
    },
    {
      "heading": "Clinical course and symptoms",
      "text": "Measles usually has an incubation period of about 11 to 12 days from exposure to the onset of the prodrome, and about 14 days from exposure to the rash, with individual values ranging from roughly one to three weeks. The prodrome lasts two to four days. Fever rises in steps, often peaking at 39.5–40.5 °C, and is accompanied by cough, coryza (runny nose), and conjunctivitis, the so-called \"three Cs.\" Early on, these symptoms can resemble other viral respiratory infections, so the prodrome alone rarely settles the diagnosis.\n\nKoplik spots are the enanthem that most distinguishes measles. They appear as small blue-white specks on a red background on the buccal mucosa, usually opposite the molars, typically 1–2 days before the rash and fading within a few days after it. Because they are transient, they can be missed when examination is delayed, and their presence in a febrile patient with the three Cs is treated as strongly suggestive of measles. Clinical diagnosis is discussed in a separate section.\n\nThe maculopapular exanthem appears 2–4 days after the prodrome begins and typically starts at the hairline and behind the ears, then spreads over the face and upper neck. Over the following three days it moves down the trunk and limbs to reach the hands and feet, with the palms and soles often spared. Individual lesions are initially distinct and blanch under finger pressure, but many become confluent, particularly on the upper body, and most no longer blanch after three to four days. The rash fades in the order it appeared and generally lasts about five to six days. In areas where it was most intense, the skin may darken and peel in fine scales. Fever and systemic symptoms often peak around the time the rash emerges, and in uncomplicated cases the illness resolves within about seven to ten days of the late prodrome.\n\nPresentation varies considerably. Severity depends on age, nutritional status, immune competence, and vitamin A status, and undernutrition or vitamin A deficiency increase the risk of severe disease and death. Among well-nourished children in high-income settings, most cases resolve without lasting effects, whereas mortality is concentrated in medically underserved populations. People with severe immunosuppression may not develop a rash at all, and their fever or rash can be delayed for weeks or months after exposure. Partially vaccinated children and adults often show an atypical picture, lacking cough, conjunctivitis, or coryza, and the illness tends to be milder and shorter.\n\nThe most striking atypical presentation is associated with the inactivated (killed) vaccine. The formalin-inactivated preparation was used in the United States between 1963 and 1967, and in some other countries into the early 1970s. Recipients were protected at first, but their immunity waned over several years. When they later encountered wild-type virus, many developed high fever, an unusual petechial or morbilliform rash beginning on the arms and legs, and severe pneumonia. Researchers in the 1960s proposed that circulating antibodies combined with delayed hypersensitivity to the virus, and the syndrome has been reported only rarely since the vaccine was withdrawn. People who received the inactivated vaccine are generally advised to receive live-attenuated vaccine doses, which protect against this reaction."
    },
    {
      "heading": "Complications and high-risk groups",
      "text": "Most measles cases end without lasting harm, but the virus can damage the lungs, the brain, and the gut, and the severity of these complications depends heavily on age, nutrition, and immune status. Pneumonia is the complication most often linked to death. The CDC describes it as the leading cause of measles death in young children, and as many as one in 20 children with measles develops pneumonia. Mayo Clinic instead groups pneumonia and encephalitis together as the two most common causes of fatal measles (4-19). Across all cases, 1 to 3 out of every 1,000 children who become infected with measles die from respiratory and neurologic complications.\n\nSecondary bacterial infections are common, particularly in children. Ear infections and diarrhea are among the most frequent non-fatal complications, and measles infection can also be complicated by secondary bacterial infections, which can cause tonsillitis, otitis media, and pneumonia. Diarrhea and vomiting in turn can lead to dehydration, which is a major reason children with measles need careful fluid management. In middle- and upper-income countries, UNICEF estimates that out of every 1,000 children who contract measles, 70 to 90 children will develop an ear infection, 80 will develop diarrhoea, and 10 to 60 will develop pneumonia.\n\nEncephalitis is rarer but more damaging. One out of every 1,000 measles cases will develop acute encephalitis, which often results in permanent brain damage. Brain inflammation can appear during the acute illness or may happen right after measles or months later. Surviving children may be left deaf or with intellectual disability. People with weakened immune systems are at particular risk of a distinct form, measles inclusion body encephalitis.\n\nSubacute sclerosing panencephalitis (SSPE) is a late, progressive disease of the central nervous system that follows measles even when the initial illness seems fully resolved. It typically develops 7 to 10 years after a person has measles. Current understanding attributes it to a persistent, mutated form of the virus that evades immune surveillance and maintains a chronic infection in the brain (10-5). Early signs are usually behavioural change and cognitive decline, followed by motor dysfunction and seizures, and the disease generally ends in death (10-6,10-7). Estimates of its frequency vary. The WHO figure of four to 11 cases per 100,000 measles cases worldwide is higher than UNICEF's figure of one in 100,000 cases, and the risk rises sharply when infection happens in infancy, with about 18 cases per 100,000 measles cases among children who contract measles early in life.\n\nSeveral groups face a higher risk of severe disease and death. The CDC lists infants and children aged <5 years, adults aged >20 years, pregnant women, and people with weakened immune systems, such as from leukemia and HIV infection among those at high risk. Infants under one year old are the single most affected group. Malnutrition, including vitamin A deficiency, also increases the chance of a fatal outcome (4-24), and people with compromised immunity are at higher risk of developing prolonged and severe disease than immunocompetent individuals.\n\nPregnancy carries risks for both mother and fetus. Measles in pregnant women can lead to pregnancy loss, premature delivery, and low birth weight. Transmission to the fetus can cause severe complications, including encephalitis and death, and is associated with a higher risk of SSPE."
    },
    {
      "heading": "Immunosuppression and immune amnesia",
      "text": "Measles causes a transient suppression of the immune system that outlasts the acute illness. The virus enters cells through CD150, a receptor found on subsets of lymphocytes, dendritic cells, macrophages and thymocytes, so infection reaches many of the cells that coordinate immune responses. MeV preferentially infects CD150-positive B cells and central and effector memory T cells, which are responsible for immunological recall responses. Because circulating cell counts are restored within weeks, the loss of cells alone cannot account for suppression that can persist for years.\n\nThe most distinctive consequence is immune amnesia, the loss of protection against pathogens the body has already met. In experimentally infected non-human primates, measles virus infects and depletes pre-existing memory lymphocytes. Studies of unvaccinated children during a Dutch outbreak extended this picture to humans. In paired blood samples collected before and after measles, investigators found reduced frequencies of circulating memory B cells and increased frequencies of regulatory T cells and transitional B cells. A later analysis of B-cell receptor sequences found that memory B cell clones present before infection were depleted in post-measles samples even after lymphocyte counts had recovered. The same work described a naive B-cell pool that had not fully rebuilt, with a profound skew toward clones with immature features in about 10% of the cohort.\n\nThese human findings have been tested in animal models. In ferrets infected with a morbillivirus used as a measles surrogate, prior vaccine-acquired protection against influenza was lost, which led to a compromised immune recall response and increased disease severity after secondary influenza virus challenge. Several mechanisms have been proposed. The leading one is the destruction of memory B and T cells, which removes the immune memory built up from earlier infections. A related hypothesis holds that pre-existing immune memory is replaced by measles-specific memory. Other proposals include impaired antigen presentation and suppression of cytokine signaling during the acute infection, and a theory of innate immune amnesia suggests that the virus erases the recollection of past exposures to microbes and \"resets\" the host's defense system back to its default.\n\nThe size and duration of the effect remain open questions. Its contribution to deaths from other diseases is especially uncertain. Reviews of the evidence note that to what extent this \"immune amnesia\" increases illness and deaths from other infections isn't clear. The concern is greatest in low-income countries, where children who survive measles may face infections such as pneumonia and diarrhea while their immune memory is depleted, and where the lack of vaccination leaves them more exposed. Clarifying these links is one reason immune amnesia is studied as a possible explanation for excess mortality following measles, rather than as an established cause."
    },
    {
      "heading": "Diagnosis and laboratory confirmation",
      "text": "Diagnosis usually starts at the bedside, but the clinical picture alone is rarely enough. The WHO describes measles as a generalized maculopapular rash that lasts three days or longer, accompanied by a temperature of at least 38.3 °C and one or more of the \"3 Cs\": cough, coryza, or conjunctivitis. Those prodromal signs are nonspecific, and mild cases can look unremarkable, so symptoms cannot be the only criterion.\n\nThe differential list is long because many febrile rash illnesses look similar. Public health guidance in Washington State names fifth disease, roseola, rubella, scarlet fever, adenovirus infection, and influenza, along with certain vector-borne illnesses, Kawasaki disease, and drug reactions. Rubella is a frequent source of confusion: its rash appears in only about half to three-quarters of cases, and it is sometimes taken for measles or scarlet fever. Dengue can be separated on the basis of the rash, which tends to begin on the trunk and move toward the face and limbs, whereas the measles rash starts on the forehead and spreads downward.\n\nSerology is the most widely used first-line test. A positive IgM result in serum drawn within the first few days after rash onset is read as presumptive evidence of recent infection. The method has limits: a result can be falsely positive, and residual IgM may still be detectable more than a year later. When an early sample is negative and PCR is also negative or not performed, a second serum sample is drawn three to ten days after symptoms begin, since some patients have not yet produced detectable antibody.\n\nMolecular confirmation rests on RT-PCR detection of measles RNA, which provides the most direct laboratory evidence of infection. Its sensitivity is highest during the first three days after the rash, although a positive result can still be obtained up to ten days later. Nasopharyngeal or throat swabs are the preferred respiratory specimens, and pairing a swab with a urine sample increases the chance of detecting the virus. Laboratories ask for synthetic rather than cotton swabs, transport media without charcoal, and cold storage during shipment. Many state public-health laboratories, along with reference centres linked to CDC and APHL, offer the assay.\n\nSequencing provides a second layer of information beyond confirmation. The WHO standard targets 450 nucleotides at the end of the nucleoprotein gene, and the resulting sequence is matched against reference sets covering 24 recognised genotypes. In settings pursuing elimination, these sequence patterns help show whether a transmission chain has been broken. Sequencing also helps separate wild-type infection from vaccine-derived virus, which matters for outbreak investigations.\n\nLaboratory work is coordinated through the WHO Global Measles and Rubella Laboratory Network, which comprises more than 700 laboratories organised into sub-national, national, regional reference, and global specialized tiers. Roughly a hundred of these laboratories carry out molecular assays for case confirmation or genotyping. A proficiency-testing program initiated by the US CDC in 2014 evaluates laboratory performance, because accurate results feed into country reports to regional verification committees. Specimens generally must be shipped cold, and in many jurisdictions the local health department has to be contacted before submission."
    },
    {
      "heading": "Treatment and post-exposure management",
      "text": "Supportive care\n\nNo specific antiviral drug is licensed for measles, so clinical management centres on easing symptoms and finding and treating complications. Medical care is supportive to help relieve symptoms. Complications, such as pneumonia and other infections, should be appropriately tested and treated. Secondary bacterial infections are treated with antibiotics, and patients are typically given fluids, nutritional support and antipyretics as needed.\n\nRibavirin, a broad-spectrum antiviral, has shown in vitro activity against MeV, but its use is limited. Although ribavirin has been used for severe MeV cases or in immunocompromised patients, strong clinical efficacy data are lacking.\n\nVitamin A\n\nThe World Health Organization recommends that all children with acute measles, regardless of their country of residence, receive vitamin A to reduce the risk of complications. Vitamin A does not block viral replication or prevent infection. Its benefit lies in reducing severe outcomes, such as eye damage, blindness and death. In deficiency-prone settings, the WHO schedule uses age-specific oral doses, and for children with clinical signs and symptoms of vitamin A deficiency, administer an additional (i.e., a third) age-specific dose of vitamin A at 2–4 weeks following the first round of dosing. Clinicians do not need to measure blood concentrations first. There is no need to measure vitamin A concentrations.\n\nIn the United States, supplementation is generally used as part of supportive care, under clinical supervision, because excess intake is harmful. Overuse of vitamin A can lead to toxicity and cause damage to the liver, bones, central nervous system, and skin. Professional guidance also states that there are no recommendations for use in other populations beyond infants and children with diagnosed measles.\n\nPost-exposure MMR vaccination\n\nFor people exposed to measles who lack adequate evidence of immunity, MMR vaccine is the preferred prophylaxis when given early. MMR administered ≤72 hours after initial exposure to measles virus might provide some protection against infection or modify the clinical course. The same window applies to health-care workers, who should receive post-exposure prophylaxis via the MMR vaccine within 72 hours of exposure. Vaccine contraindications, such as severe immunosuppression or pregnancy, still apply. For infants aged 6–11 months, MMR is preferred over IG for infants 6–11 months if given within 72 hours of exposure.\n\nImmune globulin\n\nWhen vaccination is not an option or comes too late, immune globulin is the alternative. People exposed to measles who do not have evidence of immunity may be eligible for post-exposure prophylaxis either with MMR vaccine (within 72 hours of exposure) or immunoglobulin (within 6 days of exposure). The groups at highest risk of complications include infants younger than 12 months, pregnant women, and people who have compromised immune systems, regardless of vaccination status. This extends the eligible group beyond infants and severely immunocompromised people, to pregnant women as well.\n\nSupply of this product has become more constrained over time. Measles-specific antibody levels in the population have fallen since vaccination began, so the concentration of MV-specific antibodies in immunoglobulin products derived from human plasma donors has declined as the proportion of vaccinated donors has increased. Studies of intravenous preparations used in infants during outbreaks have examined whether current products still prevent disease, and the available data on their effectiveness remain limited. Literature on the effectiveness of PEP with current available immunoglobulins is limited."
    },
    {
      "heading": "Early discovery and scientific understanding",
      "text": "Written descriptions of measles are usually traced to the Persian physician Rhazes (Abū Bakr Muhammad ibn Zakariyyā al-Rāzī), who separated the disease from smallpox. His treatise on the two illnesses was published around 910 and was later translated into more than a dozen languages. It is found in his book al-Judari wa al-Hasbah (treatise on smallpox and measles) published in 910 and translated into more than a dozen languages. Sources disagree on when the clinical description was written: some date it to the 9th century, while others place it in the 10th.\n\nFor centuries after Rhazes, European physicians often confused measles with smallpox, because both diseases produced fever and a rash. The question of what caused measles was therefore still open in the 18th century. In 1757, the Scottish physician Francis Home tested whether the illness was carried in the blood. He took blood from sick patients and introduced it through the skin of people who had never had the disease, and most of these recipients fell ill. Home based the method on the reasoning used for smallpox inoculation, which spread readily from person to person. The result pointed to a transmissible agent in the blood rather than to a condition of the patient's body alone.\n\nAnderson and Goldberger's 1911 experiments moved the question from transmission to the nature of the cause. Working at the U.S. Hygienic Laboratory, John F. Anderson and Joseph Goldberger inoculated rhesus macaques with blood and with secretions from measles patients. Roughly half of the animals developed fever, catarrhal signs and a skin eruption, which made the macaque a usable experimental model. The researchers also used filtered secretions, and the infectious material passed through the filter. This indicated that the agent was not a bacterium that could be grown on ordinary media. Broth cultures seeded with the patients' blood did not produce growth, which supported the same conclusion. The blood was infectious from before the rash appeared until roughly a day afterwards. Later work built on these findings, and the causative virus was not isolated until 1954.\n\nEpidemiological observation also contributed to the argument. Peter Panum studied an outbreak in the Faroe Islands in 1846, and his work described the incubation interval and the immunity that followed recovery. A fixed incubation period and spread through direct contact with patients were difficult to reconcile with miasma theory, which attributed epidemic disease to noxious air and environmental conditions. Contagion-based accounts of this kind therefore gained ground as an alternative explanation, and they set the stage for the viral understanding that followed."
    },
    {
      "heading": "Isolation of the virus and early vaccine development",
      "text": "The first isolation of measles virus came from an outbreak at Fay School, a boys' junior boarding school in Southborough, Massachusetts, in the winter of 1953–54. Enders got word from a colleague that there was a measles outbreak at Fay School, and he sent Thomas Peebles, a newly qualified pediatrician, to collect samples from the sick pupils. Peebles isolated the virus from some of the blood samples and throat swabs he took from students. The source of the isolate was a boy named David Edmonston. Most accounts describe him as 11 years old, although one gives his age as 13. Peebles also showed that material from the cultures could pass the disease to monkeys.\n\nThe growth of the virus in cell culture was the step that made vaccine work possible. The tissue was minced, trypsinized, and put into cell culture with nutrient media, and the virus was first grown and passed several times in primary human kidney cells. The team then moved the virus through other hosts. Passage in human amnion cells, embryonated hens' eggs, and finally chick embryo cell cultures produced virus that caused viremia and illness in kidney-passaged form, but became immunogenic without viremia or overt disease in monkeys. Chick cells were chosen partly because non-primate tissue lowered the risk of contamination with agents pathogenic to humans. The strain that resulted came to be called Edmonston, after the student from whom it was isolated.\n\nThe idea of deliberate inoculation against measles predates this work by two centuries. In 1758, during an epidemic in Edinburgh, the Scottish physician Francis Home began experimenting with inoculation. He used a mixture of blood and scrapings from the rash to inoculate roughly a dozen children through an incision in the arm. He reported fifteen attempts and claimed to have produced a mild form of the disease, while later reviewers questioned whether his subjects had actually been infected. Home's method was never widely adopted. Its limited uptake is usually attributed to the cost and difficulty of obtaining blood from sick children, and to parents who often refused. Immunization against measles had to wait until the methods of modern virology became available.\n\nEnders's team turned the Edmonston strain into a candidate vaccine in the late 1950s. Enders had been disappointed by the development of the polio vaccine and turned his attention to measles, and he formed a new team that worked on a measles vaccine for most of that decade. Clinical testing began in small groups of children between 1958 and 1960, before larger trials were carried out in New York City and Nigeria. In October 1960, the trials involved roughly 1,500 intellectually disabled children in New York City and about 4,000 children in Nigeria. Enders passed the vaccine work to Maurice Hilleman at Merck in 1960, and the first licensed live vaccine followed in 1963. The vaccine's attenuation by serial passage is discussed in the following section."
    },
    {
      "heading": "Vaccine formulations and their evolution",
      "text": "Two different products were approved in 1963, and their paths soon diverged. Regulators in the United States licensed an inactivated preparation and a live attenuated one in the same year, both an inactivated (\"killed\") and a live, attenuated (Edmonston B strain) measles vaccine. Authorities pulled the killed-virus product in 1967 after it proved to offer little protection, and some other countries continued to use the inactivated vaccine for a few years. Its failure, including the atypical illness seen in some recipients, is described under clinical course.\n\nThe live vaccine was made by repeatedly passing the virus through cultured cells. Virologists first propagated the isolate in cultured tissue from human kidneys and amnions, then transferred it to chicken embryo fibroblasts. The Edmonston B virus strain that was passaged at 35–36°C through primary renal cells, primary human amnion cells, and embryonic chicken cells a total of 59 times was used in many vaccines. This adaptation to non-human cells reduced the virus's fitness in human tissue, which is what made it safe to give to children. Further descendants followed. A live, further attenuated (Schwarz strain) vaccine was first introduced in 1965, and another live, further attenuated strain (Edmonston-Enders strain) vaccine was licensed in 1968. The original Edmonston B product was dropped in 1975 because of a relatively high frequency of fever and rash in recipients. These further attenuated vaccines caused fewer reactions than the original Edmonston B vaccine.\n\nNot all vaccine strains share one ancestry. Genomic analysis groups AIK-C, Moraten, Rubeovax, Schwarz, and Zagreb into the Edmonston lineage, whereas CAM-70, Changchun-47, Leningrad-4 and Shanghai-191 were derived from 4 different wild-type isolates. Within the Edmonston family, sequence divergence is small: vaccine viruses differed at most by 0.3% from the Edmonston wt strain. Most of the changes that do occur affect the machinery that copies the viral genome, since all of the vaccine viruses contained amino acid coding changes in the core components of the virus-encoded transcription and replication apparatus. Because the original Edmonston isolate itself is no longer available, researchers compare vaccine sequences against a laboratory wild-type that has undergone 13 passages in cell culture. Moraten and Schwarz are a notable pair, as commercial vaccine lots of Moraten and Schwarz had identical coding regions.\n\nStrains also vary by region of use and production method. Japan uses AIK-C and CAM-70, Russia uses Leningrad-16, and China uses Shanghai-191, and several of these were derived from local wild-type measles virus strains. Manufacturing methods differ as well: Schwarz/Moraten and AIK-C vaccines are produced on CEF. By contrast, Zagreg vaccine is produced on human diploid cells (WI-38). Clinical data also vary with age at administration. One trial protocol reports that vaccine effectiveness is ~ 85% when given at 9-11 months of age, and 90-95% when given at ≥12 months of age.\n\nThe Edmonston-lineage genomes have also become practical tools. Genomes encompassing the exact sequences of the vaccine strains Schwarz, Moraten, Edmonston-Zagreb, MVbv, or AIK-C are available to generate recombinant platform-based vaccines. Earlier, a 2002 review described the Schwarz/Moraten vaccine as currently the most widely used measles vaccine in the world, while Moraten alone is the strain used in the United States today, per the CDC's Moraten strain is currently used."
    },
    {
      "heading": "MMR vaccine, schedules, and safety monitoring",
      "text": "Before 1971, US measles protection relied on single-antigen products. A measles vaccine was licensed in 1963, a mumps vaccine in 1967, and a rubella vaccine in 1969 (1963: First measles vaccine licensed (US) • 1967: First mumps vaccine licensed (US) • 1969: First rubella vaccine licensed (US)). Each injection had to be given at its own visit, so scheduling problems and vaccine shortages meant that many children missed one or more doses. The combined product, developed by Maurice Hilleman at Merck, received US approval in 1971 (It was licensed for use in the US by Merck in 1971.).\n\nTwo-dose schedules came later, after measles resurged among children who had already been vaccinated. In 1989, the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) recommended that all children receive two doses of measles-containing vaccine, preferably MMR (Recurrent measles outbreaks among vaccinated school-aged children prompted both the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) in 1989 to recommend that all children receive two doses of measles-containing vaccine, preferably as MMR.). The 1989–1991 resurgence that followed produced more than 55,000 cases and greater than 120 measles-related deaths, and it was concentrated among unvaccinated preschool-aged children, particularly in urban areas. The second dose was first timed for primary or middle school entry, but the recommendation was later moved so that it is given before school entry (ACIP, the AAP, and the American Academy of Family Physicians (AAFP) now recommend that a child receive the second dose before school entry, rather than delaying it until the child is aged 11-12 years.). The current US routine gives the first dose at 12 to 15 months and the second at 4 to 6 years (ACIP recommends 2 doses of MMR vaccine routinely for children with the first dose administered at age 12 through 15 months and the second dose administered at age 4 through 6 years before school entry.). The purpose of the second dose is mainly to reach the small share of children whose first dose did not produce an immune response (The second dose of measles-containing vaccine primarily was intended to induce immunity in the small percentage of persons who did not seroconvert after vaccination with the first dose of vaccine (primary vaccine failure).).\n\nMMR is made from live but weakened viruses, and this shapes who should not receive it. The MMR vaccine is a mixture of live weakened viruses of the three diseases. Pregnancy is a contraindication, and surveillance reports have included pregnant women who were exposed to the vaccine, which is why clinicians are asked to screen patients (We identified reports of pregnant women exposed to MMR, which is a group in whom the vaccine is contraindicated, suggesting the need for continued provider education on vaccine recommendations and screening.). People with severe immunodeficiency or those receiving high-dose immunosuppressive treatment are also generally not given the live vaccine. Recently vaccinated people do not transmit the vaccine viruses to others (Being recently immunized does not increase the risk of passing measles, mumps, or rubella on to others), and there is no evidence of an association between MMR immunization and autistic spectrum disorders.\n\nSafety monitoring in the United States combines several systems. The Vaccine Adverse Event Reporting System (VAERS) was established in 1990 as a national early-warning system and is co-managed by the CDC and the FDA (Established in 1990, the Vaccine Adverse Event Reporting System (VAERS) is a national early warning system to detect possible safety problems in U.S.-licensed vaccines. VAERS is co-managed by the Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA).). Because VAERS is passive, it accepts reports from clinicians, manufacturers, and members of the public, and it has no control group, so it is subject to reporting bias, tends to underreport numbers of adverse events, lacks denominator data and unbiased comparison group, and is not designed to determine if a vaccine caused a health problem. Most reports describe minor events, since about 85–90% of vaccine adverse event reports concern relatively minor events, such as fevers or redness and swelling at the injection site. Possible signals are checked with more rigorous tools, such as the Vaccine Safety Datalink, a network of managed care sites with more than 24 million enrollees (The VSD is a network of thirteen managed care sites across the U.S. with a combined patient population of more than 24 million people.).\n\nThe commonest reactions to MMR are local and mild: pain where the vaccine is given, fever, a mild rash, and swollen glands in the cheeks or neck. Rarer events have been quantified in published studies. When first MMR and varicella shots are given separately at 12 to 23 months of age, about four will have a febrile seizure during the 7-10 days following vaccination per 10,000 children. Immune thrombocytopenia (ITP) has been linked to the six weeks after vaccination, with one study estimating 1 case per 40,000 vaccinated children. Serious allergic reactions are extremely rare."
    },
    {
      "heading": "Historical epidemics and social impact",
      "text": "Before vaccination, measles was a regular part of community life. Observers in the early twentieth century recognized that the disease returned in periodic waves, and with the exception of some isolated population groups, almost all children contracted measles before they reached adolescence. In the United States, the pattern was tightly tied to school life. Measles spread most effectively in schools, and these outbreaks led to school absences. Children in the first few grades of school had the highest infection rates. By age ten, more than 80 percent of American children had acquired the virus. Each epidemic peak came roughly every two to three years, and in the decade before the 1963 vaccine licence, the disease caused about 450 deaths a year, according to one state health department summary (approximately 3- to 4-million cases, and an average of 450 deaths a year in the U.S., with epidemic cycles occurring every 2 to 3 years).\n\nThe demographic impact was most severe where the virus had not circulated for generations. Isolated communities such as those in the Faroe Islands, Hawaii, Fiji, and Rotuma suffered devastating first-contact epidemics. The Hawaiian epidemic is recorded as wiping out 20% of the population, and one quarter of the population on the Fiji Islands died after the virus arrived in 1875. In Fiji, the epidemic followed a visit by a delegation of Fijian chiefs to Sydney, which shows how a diplomatic journey could carry a pathogen home. On Rotuma in 1911, most residents were exposed to measles virus for the first time, and cumulative measles-related mortality reached 12.8%. Among fatal cases there, gastrointestinal complications, not respiratory complications, were the predominant clinical manifestations. Because the entire community, from infants to the elderly, fell ill at the same time, few healthy people remained to provide nursing care. Researchers have proposed two explanations for the lethality: genetic susceptibility in populations that had never encountered the pathogen, and the absence of broadly protective immune responses that repeated exposure to respiratory pathogens builds up in large, well-connected populations.\n\nMortality patterns also shifted over time. Later epidemics in the same islands were often less deadly: sequential measles epidemics in Fiji produced progressively smaller case-fatality rates. More broadly, the death toll in the industrialized world had already declined sharply before vaccination. Measles mortality fell by more than 90% between the nineteenth century and the mid-twentieth century, a decline that occurred before the vaccine or routine antibiotic use for secondary infections. Factors such as pregnancy, crowding, poor nutritional status and cellular immunological impairment were repeatedly linked to high mortality.\n\nThe disease also played a role in colonial history. In the Americas, smallpox and measles led to epidemics with high mortality among Amerindians, especially during the conquest of Mexico in 1521 and of the Inca Empire in 1532. Historians have argued that such losses facilitated European conquest of the Americas, although the relative weight of disease compared with military and political factors remains a matter of scholarly debate.\n\nEpidemics of this kind also shaped the scientific and administrative response to contagious disease. During the 1846 outbreak in the Faroe Islands, the Danish physician Peter Panum examined how the virus moved through a population of roughly 7,800 people, and his work established the contagious nature of the disease and its respiratory transmission. He also noted that a dozen villages escaped infection by enacting quarantines from villages with known infections. Findings like these, together with recurring epidemics, helped establish quarantine and reporting as standard tools of public health administration, and they became foundations for later epidemiological methods."
    },
    {
      "heading": "Global immunization and mortality decline",
      "text": "The Expanded Programme on Immunization was established in 1974 through a World Health Assembly resolution that drew on the momentum of the smallpox eradication campaign. Measles was among its first targets, alongside tuberculosis, diphtheria, tetanus, pertussis and polio. The programme's importance for measles lay less in any single vaccine than in the model it provided: a routine childhood schedule, national planning and cold-chain logistics that countries could adopt. Mass measles vaccination had already begun in individual countries in the 1960s. The first internationally coordinated effort came in 1966, when WHO worked with more than 20 newly independent governments in western and central Africa, alongside USAID and the US CDC, to vaccinate against measles and to eradicate smallpox at the same time.\n\nThe Measles Initiative was formed in 2001, after the American Red Cross convened other global health organizations in February of that year to address a growing measles problem in Africa. Its founding partners were the American Red Cross, the CDC, the United Nations Foundation, UNICEF and WHO. Each partner had a distinct role. WHO set policy and guidelines for campaigns, UNICEF procured and imported vaccine for most low-income countries, the CDC supplied technical and scientific input, and the Red Cross network mobilized communities. In its first decade the initiative supported supplementary immunization campaigns in about 70 countries, reaching more than 900 million children at a cost the partners put at under US$1 per child. The partnership expanded to include rubella in 2012 and was renamed the Measles & Rubella Partnership.\n\nGlobal targets set during this period shaped the measurement of progress. The World Health Assembly committed in 2003 to halving measles deaths between 1999 and 2005, and the initiative reported a reduction of about 60 percent by the end of 2005. In 2010 the World Health Assembly set milestones of at least 90 percent national coverage with a first dose and a 95 percent reduction in deaths from the 2000 level by 2015. Estimates are revised as new data arrive, so published baselines differ. Between 2000 and 2018, WHO-related analyses reported that routine first-dose coverage rose from 72 percent to 86 percent, reported incidence fell by 66 percent, and estimated deaths fell by 73 percent, from 535,600 to 142,300. Vaccination was estimated to have averted 23.2 million deaths over that period. A later WHO assessment, using revised models, put 2000 deaths at about 780,000 and deaths in 2024 at about 95,000, an 88 percent decline, and estimated that nearly 59 million deaths had been averted since 2000.\n\nProgress has not been linear. CDC analysts noted in the mid-2000s that the rapid fall in mortality had begun to level off, raising doubts about whether the 2010 goal would be met. Between 2016 and 2018, reported incidence rose in five WHO regions, and global case numbers in 2018 were 167 percent higher than in 2016. Estimated mortality also began rising again after 2017. Gaps in coverage are concentrated among the poorest children, who tend to have weaker nutrition and limited access to health services; in 2011 more than 20 million infants did not receive a measles vaccine. Coverage shortfalls in conflict zones, remote areas and crowded urban settlements have limited the reach of these gains, and most deaths in 2024 occurred among children under five who were unvaccinated or under-vaccinated."
    },
    {
      "heading": "Elimination and eradication: definitions and verification",
      "text": "Eradication and elimination are separate goals, and they are verified differently. Eradication means the permanent cessation of transmission worldwide. Smallpox is the only human disease to have met that standard. An expert verdict in December 1979 underpinned the global declaration, which the World Health Assembly adopted in May 1980 smallpox In December 1979, an independent scientific commission certified global eradication of smallpox. This conclusion was accepted at the 33d World Health Assembly of the World Health Organization (WHO) in May 1980. Measles has not reached that threshold, so its control is judged against the narrower, regional standard of elimination.\n\nElimination is a regional designation rather than a global one. It refers to the absence of endemic transmission, meaning chains of infection that persist within a population, for at least 12 months, provided surveillance is strong enough to detect cases. PAHO's requirements for a country to be verified are broader than the time criterion alone. They include high vaccination coverage, both through routine immunization and targeted campaigns, robust surveillance systems capable of detecting and investigating suspected cases quickly, supported by molecular epidemiology (e.g., genotyping), and effective outbreak response. The evidence is assessed by the Regional Verification Commission, an independent body of public health experts appointed by the Pan American Health Organization (PAHO), which reports directly to the Director of PAHO.\n\nThe Americas were the first region of the WHO to achieve this status. Measles elimination was verified in September 2016, after rubella had been verified in April 2015. The commission that completed this work was then disbanded, and the region's status did not hold. Brazil and Venezuela lost their measles-free status in February 2019 and July 2018, respectively, which led to a new commission being formed to re-verify these countries and monitor the region. The regional status was lost again in November 2025, when after reviewing all the epidemiological data from Canada, the commission concluded that Canada lost its measles-free verification. The review of the United States and Mexico is scheduled for November 2026, during the Commission's regular annual meeting.\n\nVerification ultimately depends on whether chains of transmission can be shown to have been broken. Isolated imported cases do not by themselves determine a country's status. What matters is whether a lineage of the virus keeps circulating locally for a year or more, and this is why genotyping of viral sequences is central to the assessment."
    },
    {
      "heading": "The 2025–2026 resurgence in the Americas",
      "text": "United States\n\nMeasles returned to the United States at a scale not seen in more than three decades. As of October 8, 2026, 4,080 confirmed measles cases were reported in the United States in 2026. That is 78% above all of 2025, and it is the highest annual count since 1991 according to CDC data.\n\nCounts differ by source and date. The CDC's 2025 total appears as 2,289 confirmed measles cases in one report, while other snapshots give slightly lower figures, such as 2,285. A tracker that reported 3,887 confirmed cases as of Oct. 1 matched the federal figure reported the week before. Deaths are also counted differently: CDC recorded three confirmed measles-associated deaths in 2025, while the Pennsylvania Department of Health has reported four measles-associated deaths in 2026, and that state's later count was higher.\n\nAcross both years, over 92% of cases were in people who were unvaccinated or with unknown vaccination status, and over 9% of reported cases resulted in hospitalization. Age is also concentrated: by an early-2026 CDC snapshot, roughly three-quarters of cases involved children and young adults up to 19 years old.\n\nPennsylvania\n\nPennsylvania's outbreak became the largest in a single state in decades. Its current outbreak started in April, west of Philadelphia. The state surpassed South Carolina's outbreak earlier this year, which topped out at 997 cases. South Carolina's outbreak was contained within six months, whereas Pennsylvania's continued to grow. By October 5, the state had reported 1,004 measles cases, with 198 hospitalizations, and Lancaster County is the epicenter of the state's outbreak, with 391 cases confirmed so far. A later state update counted 1,078 measles cases across 41 Pennsylvania counties.\n\nChildren make up a large share of the Pennsylvania cases. Nearly a third of the cases have been in children, and among pediatric cases, 18% have needed hospitalization. Clinicians also reported dehydration as a common problem in young children. Fewer than 1% of the state's cases are among those who are fully vaccinated with the MMR vaccine.\n\nPockets of low coverage\n\nOutbreaks have concentrated in communities with low vaccination rates. In an earlier CDC snapshot, the largest number of cases were reported in South Carolina (670), Utah (490), Texas (182) and Florida (141). In Canada, the outbreak notably spread among certain groups of Mennonite Christians who have refused to vaccinate their children on religious grounds. Nationally, 88.5% of kindergartners in 2024 had the measles-mumps-rubella (MMR) vaccine, below the at least 95% level generally regarded as necessary to protect against outbreaks, a threshold discussed in herd immunity research. By early October, the CDC reported 42 new outbreaks in 2026, and most confirmed cases were tied to outbreaks.\n\nCanada and the regional elimination status\n\nCanada's situation changed the regional status. The outbreak that transmission continued uninterrupted since October 2024 led the Pan American Health Organization to conclude that Canada had lost its elimination status. Because when even one country in a region loses measles-elimination status, the entire region loses it. The Americas had first gained that status in 2016, lost it in 2018 after a long outbreak in Venezuela, and regained it in 2024 . Canada had held the status since 1998, and in the past year there have been more than 5,000 measles cases in the country.\n\nThe United States faces a similar assessment. The CDC is working with state and local health officials to analyze data and determine individual U.S. status. Reporting on the review indicates that the country is likely to lose its measles elimination status, which it gained in 2000, in November, when officials assess the data. Elimination status is lost if an imported case triggers a chain of transmission that continues for over a year, which is the standard that disease elimination reviews apply."
    },
    {
      "heading": "Vaccination coverage and drivers of outbreaks",
      "text": "Measles spreads so efficiently that transmission stops only when a large majority of a community is protected. The CDC notes that where fewer than 95% of people are vaccinated, one infected person can lead to roughly a dozen new infections, and the disease can cross borders to reach such communities One person infected with measles can lead to a dozen other people becoming infected in any community where less than 95% of people have been vaccinated against measles. The WHO regards routine coverage of at least 95% with two doses as the key intervention for elimination The WHO considers that achieving and maintaining percentages of routine vaccination coverage of at least 95% with two doses of the measles-containing vaccine (MCV) is the key intervention to achieve measles elimination and eradication. The figure is not a universal guarantee, however. A modelling study of measles viruses with basic reproduction numbers from 6 to 60 found that the 95% target would not be sufficient against strains with a reproduction number of 10 or more, and it proposed about 97% two-dose coverage for elimination in Europe The objective of 95% for two-dose measles vaccination coverage proposed by the WHO would not be sufficient to establish herd immunity against measles viruses with Ro ≥ 10, assuming 95% measles vaccination effectiveness. By contrast, a 97% measles vaccination coverage objective was sufficient.\n\nGlobal coverage remains short of these targets. Based on a review of immunization data, the share of children receiving a first measles dose was 83% in 2023, below the threshold needed to prevent outbreaks the proportion of children receiving the first dose of the measles vaccine at 83% in 2023, below the 95% threshold needed to prevent outbreaks.\n\nThe 2025–2026 resurgence in the United States shows how these gaps play out by age. CDC counted 4,080 confirmed cases as of October 8, 2026, and about 95% of them were unvaccinated or had unknown vaccination status the Centers for Disease Control and Prevention (CDC) reported there were 4,080* cases of measles in the US as of October 8, 2026. CDC categorized 95% of cases as unvaccinated or unknown status. The age distribution is broad. Children and adolescents aged 19 and under made up 59% of cases, while adults aged 20 and older accounted for 40% Children and adolescents aged 19 years or younger account for 59% of cases, with 710 (17%) in those younger than 5 years and 1,716 (42%) in those aged 5 to 19 years. Adults 20 years and older account for 1,635 cases (40%). Shares differ slightly across trackers and dates, but the large adult share indicates that susceptibility persists across the life course, not only in childhood.\n\nOutbreaks, however, tend to concentrate in specific communities rather than spread evenly. The 2025 Texas outbreak predominantly affected unvaccinated Mennonite communities. In 2026, Pennsylvania's outbreak became the largest single-state outbreak in more than 30 years Officials said this week that an outbreak in Pennsylvania became the largest in a single state in more than 30 years.. Non-medical exemptions for religious or philosophical reasons have likewise created under-immunization pockets, and in Massachusetts, religious exemptions are reported to be rising in certain areas religious vaccination exemptions are rising in Massachusetts, contributing to pockets of undervaccinated children in certain areas.\n\nResearchers link the decline in coverage to several overlapping factors, including access barriers, weakened routine immunization, vaccine hesitancy, misinformation, and differences in immunization policy. The recent resurgence of measles has been linked to multiple interacting factors, including lower and inconsistent vaccination coverage, vaccine hesitancy, misinformation, structural barriers to healthcare access. The COVID-19 pandemic disrupted routine services, and about 1.2 million children in the European Region missed their measles vaccine between 2020 and 2022 Between 2020 and 2022, approximately 1.2 million children in the European Region missed their measles vaccine, creating a susceptible cohort.. In the WHO African Region, the first-dose rate slipped from 70% in 2019 to 68% in 2020 In the WHO African region, MCV1 coverage declined from 70% in 2019 to 68% in 2020, while millions of children missed routine vaccination.. In high-income settings, access problems in rural areas, combined with mixed public messaging, have sustained under-vaccination in some families Access barriers in rural areas, alongside mixed public messaging, are fueling hesitancy and under-vaccination by families in these communities.\n\nBecause the factors behind measles vaccine uptake may differ from those behind other childhood vaccines, and data on how they changed after the pandemic are limited, researchers argue that behavioural and social drivers need to be measured repeatedly over time before interventions can be targeted the drivers of measles vaccine uptake are not necessarily the same as those for other childhood vaccines, and we lack data on how these drivers specifically have changed during and since the COVID-19 pandemic. Without accurately measuring the behavioural and social drivers for measles vaccination, and ideally measuring them serially over time, countries cannot design, target and implement interventions. The projected stakes of small declines are considerable: a report from the Common Health Coalition estimated that a 1% drop in the childhood MMR rate could produce about 17,000 cases a year A 1% decrease in the childhood MMR vaccination rate could cause 17,000 measles cases, 4,000 hospitalizations and 36 preventable deaths each year, according to a report from the Common Health Coalition."
    },
    {
      "heading": "Outbreak response and surveillance",
      "text": "Outbreak response starts with case investigation. Health authorities establish the rash-onset date and the infectious window of each case, then identify everyone who shared air or space with the patient during that window. Contacts are sorted by whether they have documented evidence of immunity, such as vaccination records, a laboratory-confirmed past infection, or a lab test showing immunity. Contacts without that evidence are offered MMR post-exposure doses if they can still be reached within the 72-hour window, and those who cannot be vaccinated may receive immune globulin.\n\nSusceptible contacts who do not receive prophylaxis are usually kept out of high-risk settings, such as childcare centers, schools, and healthcare facilities, rather than confined to their homes. Under US guidance, this exclusion generally runs from about day 7 after the first exposure through day 21 after the last exposure, with healthcare workers often starting on day 5. Contacts who received immune globulin, which can delay or modify illness, are excluded through day 28, because the incubation period is longer for them. Exclusion is the less restrictive of the two tools, and health departments can apply it without ordering quarantine.\n\nAn outbreak is generally declared over 42 days after the rash onset of the last case, which equals two maximum incubation periods. The clock depends on the most recent case, so a late-recognized infection restarts it. The 2025 Colorado outbreak illustrates the rule: the end was set at July 23, 2025, two incubation periods after the last infectious date of a tertiary case linked to an infectious traveler whose exposure occurred at a Denver airport. Investigators in that event traced 92 airplane contacts, of whom 74 were assessed, and they monitored contacts for 21 days using calls, text messages, or online surveys when immunity could not be verified. Shortly afterward, public health surveillance continues actively until the end date, so that any new case is detected quickly.\n\nSurveillance rests on mandatory notification, laboratory confirmation, and genomic analysis. Sequencing of viral material, usually by RT-PCR-positive specimens, allows investigators to distinguish wild-type virus from vaccine-derived virus, which matters for recently vaccinated patients with fever and rash, and to link cases into transmission chains. Matching genotypes across cases can show whether separate clusters share a common source or represent independent introductions.\n\nSome health systems now add wastewater surveillance to this toolkit, because infected people can shed measles virus in their stool before symptoms begin. In Colorado, measles virus was detected in a treatment-plant sample in early August 2025, and two cases were reported among residents of the same catchment area the following week, which suggested that the sample gave an early warning of community transmission. In Wisconsin, a wastewater assay detected a genotype D8 case before clinical reporting, but it failed to detect a case caused by genotype B3, an internationally circulating lineage. The developers then released a modified assay, which illustrates that wastewater results depend on how well an assay matches the circulating genotypes. Virginia began testing about 30 treatment plants in May 2026.\n\nBecause measles moves across state and national borders through travel, outbreak control depends on coordination among local, state, national, and international public health agencies, which share case data, genotype results, and contact lists. Clear public communication is also part of the response, since it affects whether susceptible people seek vaccination during an outbreak. Coordination failures or delayed reporting can allow transmission to continue for weeks in communities where coverage is already low."
    },
    {
      "heading": "Socioeconomic and health system impacts",
      "text": "Measles outbreaks carry direct costs that fall on health services. Each case may require hospital admission, especially for children with pneumonia or encephalitis, and even mild cases generate outpatient visits, laboratory testing, and repeated clinical assessments. Outbreak response consumes staff time for case investigation, contact tracing, and administering post-exposure doses. Because susceptible contacts must be excluded from schools and healthcare facilities for up to 21 days, a single case can trigger the isolation or monitoring of many people, and the staff who are exposed may themselves have to be removed from duty. These direct costs are often borne by local and regional public health agencies, which may have limited budgets and few spare workers.\n\nIndirect costs are often larger than the medical bill and are harder to measure. Children miss school, sometimes for several weeks, and parents or caregivers lose working days to look after sick children or to attend vaccination clinics. In communities where income is tight, these losses can translate into lost wages and reduced household resilience. The burden is therefore not only clinical: it reaches education, employment, and the household economy, and it can persist after the outbreak has been declared over.\n\nHealth systems can be strained during surges. Measles requires airborne precautions, which means that patients need single rooms, ideally with negative-pressure ventilation, and hospitals that lack such capacity may have to transfer patients or convert wards. Clinical staff must be protected and, where they are not immune, can be quarantined after exposure. Outbreak response can also divert resources away from other immunization and disease control programmes, including the routine vaccination of children against other diseases. Fieldwork, vaccine logistics, and outbreak communication compete with services that do not appear in the news, and the diversion may only become visible later, when coverage for other vaccines falls or when cases of other preventable infections rise. Measles has an additional long-term link to this problem, since survivors may lose immune memory against pathogens they had previously met, a effect discussed in the section on immunosuppression.\n\nThe burden of measles is unevenly distributed. Between countries, the largest health and economic losses have historically fallen on low-income settings, where malnutrition, limited access to hospital care, and weaker surveillance all raise the risk of death. Within countries, the burden tends to concentrate in communities with lower vaccination coverage, limited access to primary care, or geographic isolation, which means that the people least able to absorb the costs are often those most exposed. Patterns of social determinants such as income, education, and distance from services shape who is vaccinated and who receives timely treatment, so measles outbreaks can deepen existing inequalities in health.\n\nFunding for immunization in low-income countries depends heavily on international partners, including multilateral agencies, bilateral donors, and global financing mechanisms that purchase vaccines and support delivery. This dependence affects the capacity of national programmes to maintain high coverage, to replace vaccine stocks, and to finance surveillance and laboratory networks. When external financing is delayed or reduced, routine immunization can lose staff, cold-chain capacity, and outreach, and the resulting gaps in population immunity can allow measles to return even after long periods of control. Sustaining coverage therefore requires predictable funding as well as technical capacity, and this is a central concern for universal-health-coverage and for the long-term goal of elimination."
    },
    {
      "heading": "Related viruses and diseases",
      "text": "Measles virus belongs to the genus Morbillivirus, and several of its relatives infect animals. The most consequential of these is rinderpest virus, whose hosts were mainly cattle and buffalo. Rinderpest virus and measles virus are closely related morbilliviruses. Rinderpest was the second infectious disease removed from the world after smallpox, a result that came 30 years after smallpox eradication. Its elimination depended on a vaccine developed in 1960 together with a ring-vaccination approach similar to that applied to smallpox. Even after the 2011 declaration, material remained in circulation: a survey found that forty-four laboratories in 35 countries held laboratory-attenuated strains, field strains, or diagnostic samples.\n\nCanine distemper virus is a second close relative. It infects a wide range of carnivores, and both viral agents cause a similar overall pathogenesis. Because of this resemblance, researchers use it as a surrogate model for studying measles in animals whose biology permits experimental infection. The two viruses also share a host entry receptor: the SLAM molecule, which is expressed on activated T- and B-lymphocytes, as well as on dendritic cells and macrophages. Their clinical courses differ in an important respect. Infection of the central nervous system is common in canine distemper, whereas this is a rare complication in measles. Ferrets, which do not support measles infection, are highly sensitive to canine distemper virus, and this is why they are used in experimental work.\n\nRubella and mumps are unrelated to measles in the sense that matters for diagnosis. Rubella virus belongs to a different viral family altogether, and mumps virus, although also a paramyxovirus, falls into a different genus. Despite this, all three are covered by the same MMR vaccine, and their illnesses share features such as fever and rash. Clinicians must therefore distinguish them from one another, and laboratory testing is often needed to do so reliably.\n\nThe comparison with smallpox clarifies why measles is an elimination target rather than an eradication target. The only human infectious disease to be eradicated through vaccination is smallpox. Epidemiologists often describe the difference as one of geography: elimination is local, and eradication is global. Smallpox was more amenable to containment because the absence of virus transmission during the prodromal stage of infection made surveillance and isolation/containment feasible. Measles behaves differently, since cases become infectious before they become ill, so surveillance and containment cannot by themselves stop transmission and very high population immunity is needed. Measles' narrow host range, which includes humans and some non-human primates, is nonetheless what makes MeV eradication possible. Elimination is also reversible: an eliminated disease can always return if conditions allow for it."
    },
    {
      "heading": "Research frontiers and open questions",
      "text": "The mechanism of immune amnesia is still being worked out. A 2019 human study reported that measles infection removed roughly 11 to 73 percent of the antibody types a person had acquired from earlier infections, and a separate team found depletion of B cell populations in the same period. Work on unvaccinated Dutch children had earlier detected infected memory CD4 and CD8 T cells and naive and memory B cells in prodromal patients, which suggested that the virus directly reaches the cells that hold immunological memory. Open questions include how long the loss lasts, how fully survivors recover their earlier antibody repertoires through re-exposure (a process that may take months to years), and how much of the excess mortality from unrelated infections in low-income countries can be attributed to it. A NIAID-sponsored observational study in Guinea and Mali, enrolling 256 children aged 1 to 15, is designed to test these effects by comparing children with laboratory-confirmed acute infection against immune controls and by challenging both groups with a rabies vaccine.\n\nAnimal models are being used to test whether the damage can be reduced. In a study using canine distemper virus in ferrets as a surrogate for measles, an orally active paramyxovirus polymerase inhibitor, started at the onset of clinical signs, mitigated both the amnesia-like immune loss and lethal respiratory disease after earlier respiratory infections. These results are preclinical, and no licensed specific antiviral against measles exists, so care remains supportive and drug development is focused on treatment paradigms and prevention. Human trials of such a compound would need to show whether the animal benefit carries over to patients.\n\nWork on vaccine delivery aims to reach children in settings where vaccines are lost to heat exposure or inadequate cold-chain capacity. Researchers at Serum Institute of India and collaborators produced a spray-dried live attenuated measles vaccine that remained stable for about eight weeks at 37 °C, exceeding the one-week heat-stability threshold set by the World Health Organization. The key stabilizers identified were L-arginine, human serum albumin, and a combination of divalent cations. Separately, a screen of more than 11,000 liquid formulations identified candidates that lost less than one log of activity after eight hours at 40 °C, a marked improvement over commercial monovalent vaccines.\n\nMicroarray patches, which deliver vaccine through dissolving microprojections, are the most advanced alternative to needle injection. In a phase 1/2 trial in The Gambia, conducted from 2021 to 2022, 45 adults, 120 toddlers, and 120 infants were randomized, and 93 percent of infants seroconverted to measles after patch delivery, compared with 90 percent after subcutaneous injection. The trial reported no safety concerns in the first 14 days, but its sample was small and healthy participants were selected. The WHO and partners have since published a phase III framework intended to generate data for national licensure and WHO prequalification, and further studies are planned in children aged 1 to 5 years and in infants younger than nine months.\n\nImproving surveillance is a parallel priority. Serological testing can estimate population immunity, and genomic sequencing can show whether transmission chains are interrupted, but both need consistent funding and laboratory capacity to inform judgments of elimination status with greater precision. Better measurement would also clarify how far coverage must rise in specific communities, rather than only nationally, to block outbreaks and, over time, to support universal coverage of measles-containing vaccines."
    }
  ],
  "links": [
    "infectious-disease",
    "virus",
    "vaccine",
    "public-health",
    "immune-system",
    "rna",
    "b-cell",
    "t-cell",
    "dendritic-cell",
    "macrophage",
    "lymph-node",
    "antibody",
    "genome",
    "protein",
    "epidemiology",
    "diagnosis",
    "vitamin",
    "lymphocyte",
    "immunological-memory",
    "cytokine",
    "polymerase-chain-reaction",
    "world-health-organization",
    "immunodeficiency",
    "smallpox",
    "public-health-surveillance",
    "disease",
    "social-determinants-of-health",
    "universal-health-coverage",
    "health-system"
  ],
  "sources": [
    {
      "title": "Measles Virus - an overview",
      "url": "https://www.sciencedirect.com/topics/immunology-and-microbiology/measles-virus"
    },
    {
      "title": "Structural characteristics of measles virus entry - ScienceDirect",
      "url": "https://www.sciencedirect.com/science/article/abs/pii/S187962572030016X"
    },
    {
      "title": "Pathogenic measles viruses cannot evolve to bypass vaccine-induced neutralizing antibodies",
      "url": "https://www.biorxiv.org/content/10.1101/2020.10.22.351189.full.pdf"
    },
    {
      "title": "The Measles Virus Hemagglutinin β-Propeller Head β4-β5 Hydrophobic Groove Governs Functional Interactions with Nectin-4 and CD46 but Not Those with the Signaling Lymphocytic Activation Molecule",
      "url": "https://journals.asm.org/doi/10.1128/jvi.01210-13"
    },
    {
      "title": "The Receptor Attachment Function of Measles Virus Hemagglutinin Can Be Replaced with an Autonomous Protein That Binds Her2/neu While Maintaining Its Fusion-Helper Function - PMC",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC3648109/"
    },
    {
      "title": "Frontiers",
      "url": "https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2011.00247/full"
    },
    {
      "title": "Measles",
      "url": "https://health.mo.gov/book/export/html/31376"
    },
    {
      "title": "Measles Exposure",
      "url": "https://www.childrenscolorado.org/conditions-and-advice/conditions-and-symptoms/symptoms/measles-exposure/"
    },
    {
      "title": "Measles Transmission in an International Airport at a Domestic Terminal Gate — April–May 2014",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4584746/"
    },
    {
      "title": "How Measles Spreads",
      "url": "https://www.cdc.gov/measles/causes/index.html"
    },
    {
      "title": "Disease information on measles - ECDC",
      "url": "https://www.ecdc.europa.eu/en/measles/facts"
    },
    {
      "title": "Measles: Background, Pathophysiology, Etiology",
      "url": "https://emedicine.medscape.com/article/966220-overview"
    },
    {
      "title": "The basic reproduction number (R0) of measles: A systematic review",
      "url": "https://www.researchgate.net/publication/318751687_The_basic_reproduction_number_R0_of_measles_A_systematic_review"
    },
    {
      "title": "Estimating the basic reproduction number of measles in low-and middle-income settings using 172 seroprevalence studies: A modelling approach - PMC",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC13378968/"
    },
    {
      "title": "Reducing measles risk in Turkey through social integration of Syrian refugees",
      "url": "https://arxiv.org/pdf/1901.04214"
    },
    {
      "title": "Chapter 13: Measles",
      "url": "https://www.cdc.gov/pinkbook/hcp/table-of-contents/chapter-13-measles.html"
    },
    {
      "title": "Presentation",
      "url": "https://www.healio.com/clinical-guidance/measles/presentation-and-stages-of-infection-presentation-and-diagnosis"
    },
    {
      "title": "Measles Clinical Presentation: History, Physical Examination",
      "url": "https://emedicine.medscape.com/article/966220-clinical"
    },
    {
      "title": "Measles - Pediatrics - Merck Manual Professional Edition",
      "url": "https://www.merckmanuals.com/professional/pediatrics/common-viral-infections-in-infants-and-children/measles"
    },
    {
      "title": "Measles 2025",
      "url": "https://www.nejm.org/doi/full/10.1056/NEJMra2504516"
    },
    {
      "title": "Measles: A dangerous vaccine-preventable disease returns",
      "url": "https://www.ccjm.org/content/86/6/393"
    },
    {
      "title": "Measles Prevention: Recommendations of the Immunization Practices Advisory Committee (ACIP)",
      "url": "https://www.cdc.gov/mmwr/preview/mmwrhtml/00041753.htm"
    },
    {
      "title": "Measles: Clinical features",
      "url": "https://primarycarenotebook.com/pages/general-information/measles/clinical-features"
    },
    {
      "title": "Attenuated parainfluenza virus (PIV) vaccines",
      "url": "https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/7951383"
    },
    {
      "title": "Measles Data and Statistics Last updated 04/16/2019 1",
      "url": "https://www.cdc.gov/measles/downloads/measlesdataandstatsslideset.pdf"
    },
    {
      "title": "A preventable disease that's on the rise-Measles - Symptoms & causes - Mayo Clinic",
      "url": "https://www.mayoclinic.org/diseases-conditions/measles/symptoms-causes/syc-20374857"
    },
    {
      "title": "Clinical Overview of Measles",
      "url": "https://www.cdc.gov/measles/hcp/clinical-overview/index.html"
    },
    {
      "title": "How dangerous is measles?",
      "url": "https://www.unicef.org/eca/stories/how-dangerous-measles"
    },
    {
      "title": "Subacute Sclerosing Panencephalitis: Recent Advances in Pathogenesis, Diagnosis, and Treatment - PMC",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC12049210/"
    },
    {
      "title": "Measles Factsheet for healthcare professionals",
      "url": "https://www.publichealth.hscni.net/sites/default/files/2025-09/Measles%20factsheet%20FINAL.pdf"
    },
    {
      "title": "Measles Toolkit For Schools Updated: August 14, 2025",
      "url": "https://www.azdhs.gov/documents/preparedness/epidemiology-disease-control/measles/measles-school-toolkit.pdf"
    },
    {
      "title": "Subacute sclerosing panencephalitis - ScienceDirect",
      "url": "https://www.sciencedirect.com/science/article/abs/pii/S1071909125000282"
    },
    {
      "title": "Unravelling the Measles Paradox (MISIA)",
      "url": "https://clinicaltrials.gov/study/NCT07267585"
    },
    {
      "title": "Studies into the mechanism of measles-associated immune suppression during a measles outbreak in the Netherlands",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6251901/"
    },
    {
      "title": "Incomplete genetic reconstitution of B cell pools contributes to prolonged immunosuppression after measles",
      "url": "https://www.science.org/doi/abs/10.1126/sciimmunol.aay6125?intcmp=trendmd-imm&_ga=2.120392008.1586985693.1572801659-1551563515.1572801659"
    },
    {
      "title": "On invariant T cells and measles: A theory of “innate immune amnesia”",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7745983/"
    },
    {
      "title": "How measles causes the body to ‘forget’ past infections",
      "url": "https://www.science.org/doi/full/10.1126/science.366.6465.560"
    },
    {
      "title": "In Vitro Measles Virus Infection of Human Lymphocyte Subsets Demonstrates High Susceptibility and Permissiveness of both Naive and Memory B Cells",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5874404/"
    },
    {
      "title": "Manual for the Laboratory-based Surveillance of Measles, Rubella, and",
      "url": "https://cdn.who.int/media/docs/default-source/immunization/vpd_surveillance/lab_networks/measles_rubella/manual/chapter-1.pdf?sfvrsn=f7f1fc1d_2"
    },
    {
      "title": "Measles Reporting and Surveillance Guidelines",
      "url": "https://doh.wa.gov/sites/default/files/2025-08/420-063-Guideline-Measles.pdf"
    },
    {
      "title": "African Regional guidelines for measles and rubella ...",
      "url": "https://www.afro.who.int/sites/default/files/2017-06/who-african-regional-measles-and-rubella-surveillance-guidelines_updated-draft-version-april-2015_1.pdf"
    },
    {
      "title": "Dengue : Differential Diagnosis",
      "url": "https://www.mims.com/philippines/disease/dengue/differential-diagnosis"
    },
    {
      "title": "Differential Diagnosis of Scarlet Fever, Measles and Rubella",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10211225/"
    },
    {
      "title": "Laboratory Testing for Measles",
      "url": "https://www.cdc.gov/measles/php/laboratories/index.html"
    },
    {
      "title": "Measles (Rubeola) Virus, Qualitative Real-time PCR ...",
      "url": "https://testdirectory.questdiagnostics.com/test/test-guides/TS_Measles_RT_PCR/measles-rubeola-virus-qualitative-real-time-pcr-nasopharyngealthroat"
    },
    {
      "title": "Test Types Typically Available to Clinicians and ...",
      "url": "https://www.cdc.gov/mumps/media/pdfs/2025/02/MMRV-Testing-for-Clinicians_Jan2025.pdf"
    },
    {
      "title": "MEASLES LABORATORY TESTING FAQS",
      "url": "https://nj.gov/health/measles/documents/measles_lab_testing_faq.pdf"
    },
    {
      "title": "measles lab testing faq",
      "url": "https://www.nj.gov/health/cd/measles/documents/measles_lab_testing_faq.pdf"
    },
    {
      "title": "Laboratory Testing for Measles",
      "url": "https://cdc.gov/measles/php/laboratories"
    },
    {
      "title": "Whole-Genome Sequencing During Measles Outbreaks",
      "url": "https://academic.oup.com/jid/article/212/10/1529/2459182"
    },
    {
      "title": "Global Update on Measles Molecular Epidemiology",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11281501/"
    },
    {
      "title": "Building Quality Control for Molecular Assays in the Global Measles and Rubella Laboratory Network - PMC",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC11359200/"
    },
    {
      "title": "Building Quality Control for Molecular Assays in the Global Measles and Rubella Laboratory Network",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11359200/"
    },
    {
      "title": "Rubella (German measles) revisited",
      "url": "https://www.hkmj.org/system/files/hkmj187785.pdf"
    },
    {
      "title": "Healthcare Providers: Stay Alert for Measles Cases",
      "url": "https://www.cdc.gov/measles/hcp/clinical-overview/stay-alert-for-measles-cases.html"
    },
    {
      "title": "Probenecid Treatment Inhibits Replication of the Edmonston Measles Virus Strain in Vero Cells",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12656758/"
    },
    {
      "title": "Measles (Rubeola)",
      "url": "https://www.cdc.gov/yellow-book/hcp/travel-associated-infections-diseases/measles-rubeola.html"
    },
    {
      "title": "Measles, Mumps, Rubella (MMR) Vaccination and Management of Obstetric–Gynecologic Patients During a Measles Outbreak",
      "url": "https://www.acog.org/clinical/clinical-guidance/practice-advisory/articles/2024/03/management-of-obstetric-gynecologic-patients-during-a-measles-outbreak"
    },
    {
      "title": "Measles (Rubeola) Resources for Health Care Providers",
      "url": "https://www.dph.ncdhhs.gov/programs/epidemiology/communicable-disease/measles/providers"
    },
    {
      "title": "Effectiveness and Safety of an Intravenous Immune Globulin (IVIG) Preparation in Post-exposure Prophylaxis (PEP) Against Measles in Infants",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8675579/"
    },
    {
      "title": "History of measles - ScienceDirect",
      "url": "https://www.sciencedirect.com/science/article/abs/pii/S0755498222000422"
    },
    {
      "title": "Measles",
      "url": "https://historyofvaccines.org/history/measles/timeline/"
    },
    {
      "title": "History of Measles",
      "url": "https://www.cdc.gov/measles/about/history.html"
    },
    {
      "title": "History of measles - ScienceDirect",
      "url": "https://sciencedirect.com/science/article/abs/pii/S0755498222000422"
    },
    {
      "title": "Measles studies in the macaque model - PubMed",
      "url": "https://pubmed.ncbi.nlm.nih.gov/19203104/"
    },
    {
      "title": "THE CULTIVATION OF A MICROCOCCUS FROM BLOOD IN PRE-ERUPTIVE AND ERUPTIVE STAGES OF MEASLES",
      "url": "https://jamanetwork.com/journals/jama/article-abstract/442304"
    },
    {
      "title": "RECENT ADVANCES IN THE STUDY OF MEASLES VIRUS",
      "url": "https://annals.org/aim/article-abstract/677100/recent-advances-study-measles-virus"
    },
    {
      "title": "The Residence of the Infective Agent of Measles",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5194981/"
    },
    {
      "title": "Making History: David Edmonston ’57 and the Measles Vaccine",
      "url": "https://www.fayschool.org/news-detail---magazine?pk=1249137"
    },
    {
      "title": "Thomas C. Peebles",
      "url": "https://en.wikipedia.org/wiki/Thomas_C._Peebles"
    },
    {
      "title": "First disease - Measles, rubeola",
      "url": "https://litfl.com/first-disease/"
    },
    {
      "title": "Chapter 1 John F. Enders and Measles Virus Vaccine—a Reminiscence",
      "url": "https://beckassets.blob.core.windows.net/product/readingsample/183476/9783540705222_excerpt_001.pdf"
    },
    {
      "title": "John Enders",
      "url": "https://scienceheroes.com/enders-polio"
    },
    {
      "title": "Francis Home",
      "url": "https://www.rcpe.ac.uk/heritage/francis-home"
    },
    {
      "title": "Vaccines: adapting to the times - IAVI",
      "url": "https://www.iavi.org/iavi-report/vaccines-adapting-to-the-times/"
    },
    {
      "title": "Measles",
      "url": "https://circulatingnow.nlm.nih.gov/2015/03/10/measles/"
    },
    {
      "title": "John Franklin Enders",
      "url": "https://en.wikipedia.org/wiki/John_Franklin_Enders"
    },
    {
      "title": "History of measles vaccination",
      "url": "https://www.who.int/news-room/spotlight/history-of-vaccination/history-of-measles-vaccination"
    },
    {
      "title": "Measles Vaccination - Public Health - MSK Library Guides at Memorial Sloan Kettering Cancer Center",
      "url": "https://libguides.mskcc.org/publichealth/MMRvaccination"
    },
    {
      "title": "(PDF) John F. Enders and Measles Virus Vaccine—a Reminiscence",
      "url": "https://www.researchgate.net/publication/23986060_John_F_Enders_and_Measles_Virus_Vaccine-a_Reminiscence"
    },
    {
      "title": "Some vaccinated adults may not be protected against measles",
      "url": "https://www.popsci.com/measles-shot-need-re-vaccinated/"
    },
    {
      "title": "Measles, Mumps, and Rubella Vaccine - Adverse Effects of Vaccines - NCBI Bookshelf",
      "url": "https://www.ncbi.nlm.nih.gov/books/NBK190025/"
    },
    {
      "title": "(PDF) Genetic Characterization of Measles Vaccine Strains",
      "url": "https://www.researchgate.net/publication/51212585_Genetic_Characterization_of_Measles_Vaccine_Strains"
    },
    {
      "title": "Comparison of predicted amino acid sequences of measles virus strains in the Edmonston vaccine lineage - PubMed",
      "url": "https://pubmed.ncbi.nlm.nih.gov/11134304/"
    },
    {
      "title": "Measles-Rubella Vaccine Immunogenicity at 6 and 9 Months of Age",
      "url": "https://cdn.clinicaltrials.gov/large-docs/75/NCT03071575/Prot_SAP_ICF_000.pdf"
    },
    {
      "title": "Infectious cDNA of an approved vaccine strain of measles virus, use for immunogenic compositions",
      "url": "https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/9701944"
    },
    {
      "title": "Vaccine platform recombinant measles virus - PMC",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC7089060/"
    },
    {
      "title": "Recombinant measles viruses expressing epitopes of antigens of RNA viruses—use for the preparation of vaccine compositions",
      "url": "https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/9012214"
    },
    {
      "title": "Born Before 1971? Check Your MMR Immunity Status Urgently!",
      "url": "https://ubiehealth.com/doctors-note/mmr-introduction-history-prior-vaccines-measles-58101q2"
    },
    {
      "title": "MMR vaccine",
      "url": "https://en.wikipedia.org/wiki/MMR_vaccine"
    },
    {
      "title": "Measles, Mumps, and Rubella -- Vaccine Use and Strategies for Elimination of Measles, Rubella, and Congenital Rubella Syndrome and Control of Mumps: Recommendations of the Advisory Committee on Immunization Practices (ACIP)",
      "url": "https://cdc.gov/mmwr/preview/mmwrhtml/00053391.htm"
    },
    {
      "title": "Prevention of Measles, Rubella, Congenital ...",
      "url": "https://cdc.gov/mmwr/pdf/rr/rr6204.pdf"
    },
    {
      "title": "Adverse Events Following Measles, Mumps, and Rubella Vaccine in Adults Reported to the Vaccine Adverse Event Reporting System (VAERS), 2003-2013 - PubMed",
      "url": "https://pubmed.ncbi.nlm.nih.gov/25637587/"
    },
    {
      "title": "About Us - VAERs - HHS.gov",
      "url": "https://vaers.hhs.gov/about.html"
    },
    {
      "title": "Online Causal Inference with Application to Near Real-Time Post-Market Vaccine Safety Surveillance",
      "url": "https://arxiv.org/pdf/2111.13775"
    },
    {
      "title": "VAERS - Vaccine Adverse Event Reporting System - www.vaers.hhs.gov",
      "url": "https://vaers.hhs.gov/docs/VAERSDataUseGuide_en_March2025.pdf"
    },
    {
      "title": "How is Vaccine Safety Monitored in the U.S.?",
      "url": "https://www.hhs.nd.gov/sites/www/files/documents/How-is-Vaccine-Safety-Monitored-in-the-US.pdf"
    },
    {
      "title": "Measles, Mumps, Rubella (MMR) Vaccine Safety",
      "url": "https://www.cdc.gov/vaccine-safety/vaccines/mmr.html"
    },
    {
      "title": "Measles Vaccination Before the Measles-Mumps-Rubella Vaccine - PMC",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4007870/"
    },
    {
      "title": "Mass vaccination and educational attainment: Evidence from the 1967–68 Measles Eradication Campaign - ScienceDirect",
      "url": "https://www.sciencedirect.com/science/article/pii/S0167629623001054"
    },
    {
      "title": "History of Measles in Illinois",
      "url": "https://dph.illinois.gov/topics-services/diseases-and-conditions/measles/history-of-measles-in-illinois.html"
    },
    {
      "title": "History of measles - ScienceDirect",
      "url": "https://www.sciencedirect.com/science/article/am/pii/S0755498222000422"
    },
    {
      "title": "Measles - an overview",
      "url": "https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/measles"
    },
    {
      "title": "Extreme Mortality After First Introduction of Measles Virus to the Polynesian Island of Rotuma, 1911",
      "url": "https://academic.oup.com/aje/article/173/10/1211/184695"
    },
    {
      "title": "pmc.ncbi.nlm.nih.gov",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC9150958/"
    },
    {
      "title": "Extreme mortality during a historical measles outbreak on Rotuma is consistent with measles immunosuppression",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11149033/"
    },
    {
      "title": "Rapid mortality transition of Pacific Islands in the 19th century",
      "url": "https://www.cambridge.org/core/journals/epidemiology-and-infection/article/rapid-mortality-transition-of-pacific-islands-in-the-19th-century/E70299763E5A5C412744E7B510153C38"
    },
    {
      "title": "Connections from the History of Medicine Collection: Peter Panum’s Study of Measles, 1846",
      "url": "https://info.hsls.pitt.edu/updatereport/2025/december-2025/connections-from-the-history-of-medicine-collection-peter-panums-study-of-measles-1846/"
    },
    {
      "title": "Age-specific measles mortality during the late 19th-early 20th centuries - PubMed",
      "url": "https://pubmed.ncbi.nlm.nih.gov/25865777"
    },
    {
      "title": "www.cambridge.org",
      "url": "https://www.cambridge.org/core/journals/epidemiology-and-infection/article/agespecific-measles-mortality-during-the-late-19thearly-20th-centuries/F4D013C76395921C5338067A0BD0278C"
    },
    {
      "title": "Expanded Program on Immunization",
      "url": "https://en.wikipedia.org/wiki/Expanded_Programme_on_Immunization"
    },
    {
      "title": "Contribution of vaccination to improved survival and health: modelling 50 years of the Expanded Programme on Immunization - ScienceDirect",
      "url": "https://www.sciencedirect.com/science/article/pii/S014067362400850X"
    },
    {
      "title": "Measles & Rubella Initiative",
      "url": "https://en.wikipedia.org/wiki/Measles_&_Rubella_Initiative"
    },
    {
      "title": "Evolution and Contribution of a Global Partnership against Measles and Rubella, 2001–2023",
      "url": "https://doi.org/10.3390/vaccines12060693"
    },
    {
      "title": "timeline-p - Measles & Rubella Partnership",
      "url": "https://measlesrubellapartnership.org/timeline-p/"
    },
    {
      "title": "Measles",
      "url": "https://www.who.int/news-room/fact-sheets/detail/measles"
    },
    {
      "title": "Measles deaths down 88% since 2000, but cases surge - PAHO/WHO",
      "url": "https://www.paho.org/en/news/28-11-2025-measles-deaths-down-88-2000-cases-surge"
    },
    {
      "title": "Progress Toward Regional Measles Elimination — Worldwide, 2000–2018",
      "url": "https://www.cdc.gov/mmwr/volumes/68/wr/mm6848a1.htm"
    },
    {
      "title": "Global Measles Mortality, 2000--2008",
      "url": "https://www.cdc.gov/mmWr/preview/mmwrhtml/mm5847a2.htm"
    },
    {
      "title": "cdc 27494 DS1",
      "url": "https://stacks.cdc.gov/view/cdc/27494/cdc_27494_DS1.pdf"
    },
    {
      "title": "The confirmation and maintenance of smallpox eradication - PubMed",
      "url": "https://pubmed.ncbi.nlm.nih.gov/6252467/"
    },
    {
      "title": "Measles and Rubella Elimination Regional Monitoring and Re-Verification Commission - PAHO/WHO",
      "url": "https://www.paho.org/en/measles-rubella-elimination-regional-monitoring-re-verification-commission"
    },
    {
      "title": "Measles elimination status in the United States and Mexico - PAHO/WHO",
      "url": "https://www.paho.org/en/news/16-1-2026-measles-elimination-status-united-states-and-mexico"
    },
    {
      "title": "Sustaining the Elimination of Measles, Rubella and Congenital Rubella Syndrome in the Americas, 2019–2023: From Challenges to Opportunities - PMC",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC11209250/"
    },
    {
      "title": "Sustaining measles and rubella elimination through the Regional Monitoring and Re-Verification Commission in the Americas",
      "url": "https://journal.paho.org/en/articles/sustaining-measles-and-rubella-elimination-through-regional-monitoring-and-re-verification"
    },
    {
      "title": "Measles resurgence in the Americas",
      "url": "https://en.wikipedia.org/wiki/Measles_resurgence_in_the_Americas"
    },
    {
      "title": "Update on the review of measles elimination status - PAHO/WHO",
      "url": "https://www.paho.org/en/news/2-3-2026-update-review-measles-elimination-status"
    },
    {
      "title": "PAHO calls for regional action as the Americas lose measles elimination status - PAHO/WHO",
      "url": "https://www.paho.org/en/news/10-11-2025-paho-calls-regional-action-americas-lose-measles-elimination-status"
    },
    {
      "title": "Measles Cases and Outbreaks",
      "url": "https://www.cdc.gov/measles/data-research/index.html"
    },
    {
      "title": "Measles Update: October 9, 2026",
      "url": "https://www.contagionlive.com/view/measles-update-october-9-2026"
    },
    {
      "title": "U.S. Measles Outbreaks 2025-2026: Overview and Issues for Congress - EveryCRSReport.com",
      "url": "https://www.everycrsreport.com/reports/IF13322.html"
    },
    {
      "title": "US measles outbreak approaches 1,500 cases",
      "url": "https://www.cidrap.umn.edu/measles/us-measles-outbreak-approaches-1500-cases"
    },
    {
      "title": "Tracking US Measles in 2026: 3,887 Cases Put Elimination Status at Risk",
      "url": "https://www.usnews.com/news/health-news/articles/tracking-the-2026-u-s-measles-outbreaks"
    },
    {
      "title": "Pennsylvania’s measles outbreak is the largest in decades in the U.S.",
      "url": "https://www.ms.now/news/pennsylvania-measles-outbreak-iargest-decades"
    },
    {
      "title": "Pennsylvania’s measles outbreak is the country’s largest in three decades",
      "url": "https://www.nbcnews.com/health/health-news/pennsylvanias-measles-outbreak-countrys-largest-three-decades-rcna601648"
    },
    {
      "title": "Measles cases surpass 1,000 in Pennsylvania amid the state's largest outbreak in decades - ABC News",
      "url": "https://abcnews.com/Health/measles-cases-surpass-1000-pennsylvania-outbreak-continues-spread/story?id=137002024"
    },
    {
      "title": "Pa. measles outbreak becomes largest, deadliest in country over last 30 years",
      "url": "https://www.wfmz.com/news/area/pennsylvania/pa-measles-outbreak-becomes-largest-deadliest-in-country-over-last-30-years/article_c428d1e4-e414-4fbf-a5a4-51a3f9519a85.html"
    },
    {
      "title": "CDC: 43 additional measles cases reported as 2026 total approaches 91% of last year’s count",
      "url": "https://publications.aap.org/aapnews/news/35345/CDC-43-additional-measles-cases-reported-as-2026"
    },
    {
      "title": "Deadly measles surge sees Canada lose eradicated status",
      "url": "https://gulfnews.com/world/americas/deadly-measles-surge-sees-canada-lose-eradicated-status-2-1.500341849"
    },
    {
      "title": "Pennsylvania’s measles outbreak is the country’s largest in three decades - AOL",
      "url": "https://www.aol.com/articles/pennsylvania-measles-outbreak-country-largest-213758000.html"
    },
    {
      "title": "Canada loses its measles elimination status amid large outbreak",
      "url": "https://www.cnn.com/2025/11/10/health/canada-measles-elimination-status-removed"
    },
    {
      "title": "Canada loses measles elimination status — as does the entire Americas region",
      "url": "https://www.statnews.com/2025/11/10/measles-canada-americas-paho-who-elimination-status/"
    },
    {
      "title": "Canada loses measles elimination status after record year of outbreaks",
      "url": "https://www.cidrap.umn.edu/measles/canada-loses-measles-elimination-status-after-record-year-outbreaks"
    },
    {
      "title": "Understanding Current U.S. Measles Outbreaks and Elimination Status",
      "url": "https://www.astho.org/communications/blog/2026/understanding-current-us-measles-outbreaks-elimination-status/"
    },
    {
      "title": "About Global Measles",
      "url": "https://www.cdc.gov/global-measles-vaccination/about/index.html"
    },
    {
      "title": "Measles Vaccination Coverage and Anti-Measles Herd Immunity Levels in the World and WHO Regions Worsened from 2019 to 2023",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11860562/"
    },
    {
      "title": "Are the Objectives Proposed by the WHO for Routine Measles Vaccination Coverage and Population Measles Immunity Sufficient to Achieve Measles Elimination from Europe?",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7349949/"
    },
    {
      "title": "Global Resurgence of Measles: Turning the Tide through a Bold Agenda for Prevention and Control - International Journal of Infectious Diseases",
      "url": "https://www.ijidonline.com/article/S1201-9712(25)00124-9/fulltext"
    },
    {
      "title": "2025 Southwest United States measles outbreak",
      "url": "https://en.wikipedia.org/wiki/2025_Southwest_United_States_measles_outbreak"
    },
    {
      "title": "Measles Resurgence and the Fragility of Herd Immunity: Implications for Pediatric Infectious Disease Practice",
      "url": "https://academic.oup.com/jpids/article/14/11/piaf094/8292621"
    },
    {
      "title": "Massachusetts Faces Measles Risk as Some Counties Fall Below Vaccination Threshold - 105.7 WROR",
      "url": "https://wror.com/2026/10/08/massachusetts-faces-measles-risk-as-some-counties-fall-below-vaccination-threshold/"
    },
    {
      "title": "Challenges to sustaining measles elimination: transmission dynamics, immunity gaps, and resurgence in post-elimination settings",
      "url": "https://academic.oup.com/rescon/article/1/3/vmag107/8721592"
    },
    {
      "title": "Drivers of measles resurgence in Africa: Strategies to increase vaccine coverage in remote communities [Perspective] - JIEPH",
      "url": "https://afenet-journal.org/10-37432-jieph-d-26-00243/"
    },
    {
      "title": "The Case for Assessing the Drivers of Measles Vaccine Uptake",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11209301/"
    },
    {
      "title": "Measles and public health: an integrative approach - PMC - NIH",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC12522929/"
    },
    {
      "title": "Chapter 7: Measles",
      "url": "https://www.cdc.gov/surv-manual/php/table-of-contents/chapter-7-measles.html"
    },
    {
      "title": "Measles Investigation Quicksheet - CDPH",
      "url": "https://www.cdph.ca.gov/Programs/CID/DCDC/CDPH%20Document%20Library/Immunization/Measles-Quicksheet.pdf"
    },
    {
      "title": "Measles Outbreak Associated with an Infectious Traveler — Colorado, May–June 2025",
      "url": "https://www.cdc.gov/mmwr/volumes/75/wr/mm7504a1.htm?s_cid=OS_mm7504a1_w"
    },
    {
      "title": "Michigan State and Local Public Health Measles Standard Operating Procedures 1",
      "url": "https://www.michigan.gov/mdhhs/-/media/Project/Websites/mdhhs/Folder1/CD_Info/A-Z/Measles_SOP.pdf?rev=608dd9a106a34436b8befabdbe51c136&hash=76024C639C559859A2D70BF87BF90CF1"
    },
    {
      "title": "Notes from the Field: Wastewater Surveillance for Measles Virus During a Measles Outbreak — Colorado, August 2025",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12806976/"
    },
    {
      "title": "Genotype-Specific Detection of Measles Virus Using Wastewater Surveillance — Wisconsin, February 2026",
      "url": "https://www.cdc.gov/mmwr/volumes/75/wr/mm7527a1.htm"
    },
    {
      "title": "Measles Wastewater Monitoring - Virginia Department of Health",
      "url": "https://www.vdh.virginia.gov/blog/2026/05/26/measles-wastewater-monitoring/"
    },
    {
      "title": "Rinderpest - an overview",
      "url": "https://www.sciencedirect.com/topics/veterinary-science-and-veterinary-medicine/rinderpest"
    },
    {
      "title": "Rinderpest Virus Sequestration and Use in Posteradication Era - PMC",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC3557999/"
    },
    {
      "title": "How rinderpest was eradicated",
      "url": "https://ourworldindata.org/how-rinderpest-was-eradicated"
    },
    {
      "title": "Tropism and molecular pathogenesis of canine distemper virus - PMC",
      "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC6407191/"
    },
    {
      "title": "Morbillivirus Experimental Animal Models: Measles Virus Pathogenesis Insights from Canine Distemper Virus",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5086610/"
    },
    {
      "title": "Lethal Canine Distemper Virus (Morbillivirus canis) Outbreak in Free-Ranging Black-Tufted Marmosets (Callithrix penicillata) in Brazil: Clinical, Pathological, Genotypical Evaluation, and Assessment of Viral Tropism",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12629703/"
    },
    {
      "title": "Disease Elimination and Eradication",
      "url": "https://historyofvaccines.org/vaccines-101/what-do-vaccines-do/disease-elimination-and-eradication/"
    },
    {
      "title": "Why public health officials have only ever eradicated one disease",
      "url": "https://www.popsci.com/infectious-disease-eradication-measles-smallpox/"
    },
    {
      "title": "Smallpox Eradication - an overview",
      "url": "https://www.sciencedirect.com/topics/immunology-and-microbiology/smallpox-eradication"
    },
    {
      "title": "Disease elimination vs. eradication",
      "url": "https://healthjournalism.org/glossary-terms/disease-elimination-vs-eradication-2/"
    },
    {
      "title": "Morbillivirus Infections: An Introduction",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4353911/"
    },
    {
      "title": "Rinderpest - Information - AGES",
      "url": "https://www.ages.at/en/human/disease/pathogens-from-a-to-z/rinderpest"
    },
    {
      "title": "Rinderpest: The Second Disease to Be Eradicated in the World",
      "url": "https://www.gideononline.com/blogs/rinderpest-virus-historical-impact-and-eradication/"
    },
    {
      "title": "Rinderpest - Generalized Conditions - Merck Veterinary Manual",
      "url": "https://www.merckvetmanual.com/generalized-conditions/rinderpest/rinderpest"
    },
    {
      "title": "Morbillivirus - an overview",
      "url": "https://www.sciencedirect.com/topics/immunology-and-microbiology/morbillivirus"
    },
    {
      "title": "Inside Immune Amnesia",
      "url": "https://hms.harvard.edu/news/inside-immune-amnesia"
    },
    {
      "title": "Measles Infection Weakens Global Immune Defenses, Say Studies",
      "url": "https://www.aafp.org/news/health-of-the-public/20191119measlesimmunity.html"
    },
    {
      "title": "Studies into the mechanism of measles-associated immune suppression during a measles outbreak in the Netherlands",
      "url": "https://www.nature.com/articles/s41467-018-07515-0"
    },
    {
      "title": "Investigating immune amnesia after measles virus infection in two West African countries: A study protocol",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12200839/"
    },
    {
      "title": "Therapeutic mitigation of measles-like immune amnesia and exacerbated disease after prior respiratory virus infections in ferrets",
      "url": "https://www.nature.com/articles/s41467-024-45418-5"
    },
    {
      "title": "Heat-stable measles vaccine produced by spray drying - PubMed",
      "url": "https://pubmed.ncbi.nlm.nih.gov/19944152"
    },
    {
      "title": "Towards ambient temperature-stable vaccines: The identification of thermally stabilizing liquid formulations for measles virus using an innovative high-throughput infectivity assay - ScienceDirect",
      "url": "https://www.sciencedirect.com/science/article/pii/S0264410X11006347"
    },
    {
      "title": "A measles and rubella vaccine microneedle patch in The Gambia: a phase 1/2, double-blind, double-dummy, randomised, active-controlled, age de-escalation trial",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11099471/"
    },
    {
      "title": "Measles–Rubella Microarray Patches Phase III Clinical Trial Framework: Proposal and Considerations",
      "url": "https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11598609/"
    }
  ],
  "license": "https://creativecommons.org/licenses/by/4.0/"
}