Gastroenteritis is an inflammation of the stomach and intestines that causes diarrhea, vomiting, nausea and other symptoms of digestive upset. In the industrialized world, the most common causes of gastroenteritis in children are viruses, bacteria (food poisoning), and intestinal parasites.
Viral gastroenteritis – In otherwise healthy children, viral infections of the digestive tract often are responsible for mild episodes of gastroenteritis. In the United States, the most common causes of viral gastroenteritis in children are rotaviruses, adenoviruses, enteroviruses (during summer months), astroviruses and Norwalk-like virus (norovirus). Rotaviruses are the most likely cause of infectious diarrhea in children under age 5. All of these viruses tend to spread on hands that have touched either an infected person's stool or surfaces contaminated with infected stool. For this reason, young children – especially those just starting to learn good hygiene – are particularly vulnerable to viral gastroenteritis. They may touch a dirty diaper (either their own or a playmate's), forget to wash their hands after using the toilet, put dirty fingers in their mouths, bite their fingernails, or chew and suck on toys that other children have touched with soiled hands. Parents and child-care personnel also can spread viral gastroenteritis from child to child, particularly if they do not wash their hands thoroughly with soap and water after changing every soiled diaper. In addition, adults who have viral gastroenteritis themselves sometimes can spread their viral infections to children, especially if they prepare children's meals without first washing their hands with soap and water. Occasionally, some of the viruses that cause viral gastroenteritis also have been found in drinking water or food, primarily in developing countries and rural areas where sanitation is poor. Norovirus has gotten plenty of press in recent years, mostly because of outbreaks of Norwalk-like viruses on cruise ships.
Bacterial gastroenteritis (food poisoning) – Food that hasn't been prepared or stored properly can grow bacteria on its surface, and these bacteria sometimes produce irritating chemicals called toxins. If a child eats the germ-filled food, symptoms of gastroenteritis are triggered either by the bacteria themselves or by their irritating byproducts. In addition, certain types of aggressive bacteria, such as Campylobacter, Salmonella or E. coli 0157, can cause more severe forms of food poisoning that produce high fever, severe gastrointestinal symptoms and dehydration, even in children who are usually strong and healthy.
Intestinal parasites – Intestinal parasites can be spread to children on dirty hands, on the soiled surfaces of toys and bathroom fixtures, and in contaminated water or food. Giardia lamblia, the parasite that causes giardiasis, is the most common parasitic cause of diarrhea among children in the United States, especially those in child care centers.
Worldwide, gastroenteritis kills millions children every year, primarily in developing nations where sanitation and health care are poor. Most of these children die from extreme dehydration (abnormally low levels of body water) resulting from a combination of severe diarrhea, vomiting and not drinking enough fluids. Even in the industrialized world, millions of episodes of gastroenteritis occur each year, especially in young children. In the United States, rotavirus infections used to be responsible for more than 3 million cases of gastroenteritis in children each year, with at least 50,000 hospitalizations and 20 to 40 deaths. Fortunately, the rotavirus vaccine that is given to young infants has been very effective in decreasing the number of moderate to severe cases of rotavirus disease in the United States.
Overall, about 90% of children with gastroenteritis in the United States have such mild symptoms that they do not need to be treated by a doctor. Occasionally, however, gastroenteritis can lead to severe dehydration and other dangerous complications. This is more likely to happen in infants, children with chronic illnesses and children taking immune-suppressing medications.