Diarrhea is a condition in which a person passes loose or liquid stools more often than is usual for that person. It is a symptom rather than a single disease, and it arises from many causes, the most important of which in global public health are infections. Most episodes are short and resolve without specific treatment, but severe episodes can cause fatal dehydration, especially in infants and young children.
Definition and classification
A common working definition counts three or more loose or liquid stools in a day as diarrhea, or any stooling noticeably more frequent than a person's normal pattern Diarrhoea is defined as the passage of three or more loose or liquid stools per day, or more frequently than is normal for the individual.
Clinically, the World Health Organization distinguishes three types. Acute watery diarrhea, which resolves within hours or days, includes cholera. Acute bloody diarrhea is also called dysentery. Persistent diarrhea continues for 14 days or longer acute watery diarrhoea – lasts several hours or days, and includes cholera; acute bloody diarrhoea – also called dysentery; and persistent diarrhoea – lasts 14 days or longer. Separately, clinicians commonly call diarrhea chronic when it lasts beyond about four weeks, a threshold tied to the range of non-infectious causes that must then be considered.
Epidemiology and burden
Diarrheal disease is one of the leading killers of children under five. Current WHO figures place it in third position, with about 443,832 deaths of children under five each year Each year diarrhoea kills around 443 832 children under 5 and an additional 50 851 children aged 5 to 9 years. Earlier WHO editions ranked it second, and the number of deaths in those editions was higher Diarrhoeal disease is the second leading cause of death in children under five years old. A systematic analysis estimated that child diarrhea deaths fell from about 1.2 million in 2000 to about 444,000 in 2021, although the study attributed a specific cause to most of these deaths We could attribute a cause to 1 003 448 (83·8%) of the estimated 1 197 044 global deaths from diarrhoea in children younger than 5 years in 2000 and 360 730 (81·3%) of the estimated 443 833 global deaths from diarrhoea in children younger than 5 years in 2021.
The burden is strongly unequal. Over 99% of diarrhoea mortality in under-five children occurs in low- and middle-income countries, and Sub-Saharan Africa and Southeast Asia bear most of the global diarrhoeal burden, accounting for > 80% of under-five deaths from the disease. Worldwide, the number of episodes is very large. Globally, there are nearly 1.7 billion cases of childhood diarrhoeal disease every year. Repeated episodes also carry consequences beyond the acute illness, including undernutrition, weakened immunity, and impaired cognitive development repeated bouts of acute diarrhoea, as well as chronic and persistent diarrhoea, have long-term health consequences, including undernutrition, weakened immune systems, impaired cognitive development, and a higher risk of cardiometabolic diseases in adulthood. Diarrhea is also a major contributor to malnutrition in young children, which in turn increases vulnerability to further episodes.
Causes
Infectious causes
Most diarrhea in low-income settings is infectious. The organisms are mainly viral, bacterial, and parasitic, and many are transmitted through contaminated food and water. viral and parasitic organisms, most of which are spread by faeces-contaminated water. The main pathogens are listed in bacterial, viral, and protozoan groups. Among children under five, rotavirus has been the largest estimated single cause of diarrhea deaths for two decades, and cholera is a major cause of epidemic watery diarrhea. The relative importance of pathogens has shifted over time. in 2021, Shigella sp had the second largest estimated attribution in LMICs, while norovirus remained the second-largest cause in high-income countries. Bacterial infections that spread into the bloodstream are also an increasing share of deaths other causes such as septic bacterial infections are likely to account for an increasing proportion of all diarrhoea-associated deaths.
Non-infectious causes
Diarrhea also arises from many non-infectious conditions. These include inflammatory bowel disease (see inflammatory-bowel-disease), malabsorption of sugars or fats, lactose intolerance, certain medications, and overactive thyroid function. Diarrhea can also be a side effect of antibiotics, which disturb the intestinal microbiota and can allow overgrowth of organisms such as Clostridioides difficile.
Risk factors
Infection is much more common where clean water is scarce for drinking, cooking, and cleaning. Infection is more common when there is a shortage of clean water for drinking, cooking and cleaning. Malnutrition and impaired immunity greatly increase the risk of severe disease. Children who are malnourished or have impaired immunity as well as people living with HIV are most at risk of life-threatening diarrhoea.
Pathophysiology
The intestine normally absorbs most of the water and electrolytes that pass through it. Diarrhea results when this balance is disturbed in one or more of several ways:
- Secretory diarrhea: The intestinal lining actively secretes water and electrolytes. Cholera toxin is a classic example, and it drives chloride and water into the gut lumen.
- Osmotic diarrhea: Poorly absorbed solutes, such as sugars or magnesium salts, draw water into the bowel. This type typically stops when fasting.
- Inflammatory (exudative) diarrhea: Infection or inflammation damages the mucosa, causing leakage of fluid, mucus, and blood. This pattern is typical of dysentery.
- Dysmotility: Rapid transit through the gut reduces the time available for water absorption.
Dehydration is the main mechanism of death. Diarrhoea can last several days, and can leave the body without the water and salts that are necessary for survival. In the past, dehydration and fluid loss caused most diarrhea deaths In the past, for most people, severe dehydration and fluid loss were the main causes of diarrhoea deaths.
Diagnosis and assessment
Assessment usually begins with the pattern and duration of stools, the presence of blood or fever, recent travel or food exposure, medication use, and signs of dehydration. Stool testing can identify specific pathogens, though results depend on the method used. Some laboratory methods are less sensitive than molecular tests, so pathogen estimates from older studies may be underestimates. In children, the degree of dehydration is central to deciding how urgently care is needed.
Treatment
Oral rehydration
The central treatment is replacing fluid and electrolytes. Oral rehydration solution (ORS) is a glucose-and-salt mixture. Oral rehydration solution (ORS) is a type of fluid replacement used to prevent and treat dehydration due to diarrhea. The use of ORS for diarrhea has been recommended by WHO and UNICEF since the 1970s, and the two organizations updated their guidance in 2004 WHO and UNICEF have recommended the use of ORS for the treatment of diarrhea since the 1970's and, in 2004, the two organizations released the Joint Statement for Clinical Management of Acute Diarrhea updating their recommendations.
ORS does not shorten the illness or reduce stool output. ORS, however, does not reduce the volume or frequency of stool output in diarrhea. Its value lies in preventing dehydration, which is why it is called oral rehydration therapy (ORT) when combined with continued feeding.
Zinc
Zinc supplementation is a second, adjunct treatment. In a meta-analysis of 16 trials that included 15,231 participants with acute diarrhea and 6 trials that included 2,968 participants with persistent diarrhea, zinc supplementation resulted in a reduction of the mean duration of both acute and persistent diarrhea as well as a reduction in stool frequency. The WHO recommends oral zinc for 10-14 days at 20 mg per day in children older than 6 months and 10 mg per day in children younger than 6 months for acute diarrheal illness. Zinc does not have a specific recommended regimen for adults, owing to limited data.
Other treatments
Antimotility drugs such as loperamide have been restricted in children because of reports of serious adverse reactions. Antibiotics are used only for specific pathogens or severe cases, since their use can select for antibiotic-resistant organisms. Most acute diarrhea in high-income settings resolves without antibiotics.
Prevention
Much childhood diarrhea is preventable. A significant proportion of diarrhoeal disease can be prevented through safe drinking-water and adequate sanitation and hygiene. Vaccination is an important tool. The introduction of rotavirus vaccines reduced severe rotavirus diarrhea in children by about 40% in low- and middle-income countries between 2008 and 2016 The introduction of rotavirus vaccines into national immunisation programmes decreased severe rotavirus diarrhoea in children by approximately 40% in low-income and middle-income countries (LMICs) from 2008 to 2016. Other measures include breastfeeding, vitamin A supplementation, and improving water and sanitation practices promotion of breastfeeding, vitamin A supplementation, immunization against rotavirus – a leading cause of diarrhoea – and proven methods of improving water, sanitation and hygiene practices.
Limitations and debates
Treatment gaps. Recommended treatment is far from universal. A 2009 WHO/UNICEF report found only 44% of children with diarrhoea in low-income countries receive the recommended treatment, and limited trend data suggest that there has been little progress since 2000.
Trends. Assessments of progress differ. The 2009 report above described little progress since 2000, whereas a 2024 analysis of pathogen-specific deaths concluded that there is progress in the reduction of deaths from diarrhoea caused by 12 pathogens in children younger than 5 years in the past two decades.
Estimation uncertainty. Global death counts and pathogen attributions are modelled estimates, drawn from a limited number of studies and adjusted for diagnostic sensitivity, and their confidence intervals overlap for some pathogens.
Antimicrobial resistance and bloodstream infection. The growing role of invasive bacterial infection in diarrhea deaths complicates treatment, since it cannot be managed by rehydration alone and depends on antibiotic access and effectiveness.
Diagnosis and prevention in high-income settings. Non-infectious causes and the value of routine testing are discussed in clinical practice guidelines, and debates continue over how aggressively to test and treat acute diarrhea in adults and older children.
References
- Diarrhoeal Diseases (BI0103)undrr.org
- 22/08/2023, 16:13 Diarrhoeal diseaseuts.edu.au
- Diarrhoeal diseasewho.int
- Estimated global and regional causes of deaths from diarrhoea in children younger than 5 years during 2000–21: a systematic review and Bayesian multinomial analysisncbi.nlm.nih.gov
- Impact of climate change on diarrhoea risk in low- and middle-income countriesmedrxiv.org
- Diarrhoeal disease: WHO Fact sheet N?330 - FluTrackers News and Informationflutrackers.com
- Oral Rehydration Solution (ORS) and Zincgivewell.org
- Oral Zinc for the Treatment of Acute Diarrhea in US Childrenclinicaltrials.gov
- Recent Advances of Oral Rehydration Therapy (ORT) - PMCpmc.ncbi.nlm.nih.gov
- Aetiology and incidence of diarrhoea requiring hospitalisation in children under 5 years of age in 28 low-income and middle-income countries: findings from the Global Pediatric Diarrhea Surveillance networkncbi.nlm.nih.gov
- Diarrhoea : Why children are still dying and what can be donedata.unicef.org
- Diarrhoea: Why children are still dying and what can be donewho.int