Gastroenteritis, also described as inflammation of the gastrointestinal tract, is a sickness of fever, diarrhea and vomiting caused by an infectious virus, bacterium or parasite. It typically is of acute onset, usually lasting less than 10 days and self-limiting. Every so often it is referred to just as 'gastro'. It is often named the stomach flu or gastric flu even though it is not related to influenza.

If only the inflammation is found in the stomach, the term gastritis is used, and if only the small bowel is affected it is called enteritis.

Bacterial causes
Bacterial causes are less common in developed countries. Campylobacter jejuni is responsible for 5-10% of all cases, whereas Salmonella species, Shigella species, and various pathogenic types of Escherichia coli is accounted for a tiny percentage.

In the developing world enterotoxigenic, enteropathogenic and enteroinvasive E. coli are essential due to the sheer number of cases, whereas Shigella causes debilitating sickness and has increasing resistance against low-priced and readily available antibiotics. Cholera, caused by Vibrio cholerae is one more important cause of acute diarrhea sickness and following death in the developing world.

Viral causes
Viral causes are the most common of acute gastroenteritis (AGE) in children less than 5 years of age, in both developed countries and developing countries. Rotavirus group A (up to 50% of the cases), noroviruses (the most common cause of outbreaks of AGE in all age groups), adenoviruses type 40 and 41, astrovirus, and finally sapovirus.

Parasites
An outbreak of Giardia lamblia can cause dehydrating diarrhea in infants, and Cryptosporidium is known to cause 1-4% of cases of acute diarrhea in hospitalized infants.

Epidemiology
Worldwide diarrhea caused 4.6 million deaths in children in 1980 alone, and most of these in the developing world. This figure has now come down considerably to approximately 1.5 million deaths yearly, mainly due to global introduction of correct oral rehydration therapy (Victora et al 2000).

The commonness in the developed countries is as high as 1-2.5 cases per child per year and a major cause of hospitalization in this age group.

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