Table 1B.

Clinical and epidemiological characteristics of the main viral enteropathogens

Pathogen	Typical age at presentation	Type of diarrhea	Duration of symptoms	Clinical features	Transmission	Seasonality
Adenovirus (enteric serotypes 40, 41)	Primarily affects children younger than 2 years	Watery diarrhea	Adenovirus infections are most communicable during the first few days of an acute illness, but persistent and intermittent shedding for longer periods (mean 10 days) is common.	Vomiting. High fever (over 39°C) is uncommon. Asymptomatic infections are common, and reinfections can occur	Transmitted by direct contact, fecal-oral transmission, and occasionally waterborne transmission	The adenovirus activity peak is in winter and spring seasons (December–March)
Astrovirus (Astroviridae family)	Children < 4 years	Copious, watery diarrhea	5–6 days	Abdominal pain, vomiting, nausea, fever, malaise	Astrovirus is most frequently transmitted through a fecal-oral route. Contaminated food, water, or fomites have been suspected in several outbreaks	Winter
Caliciviridae family (genus Calicivirus)
Norovirus (species called Norwalk virus)	Children < 5 years of age (predominant between 12 and 24 months)	Watery diarrheal disease	Symptoms usually last for 24–60 hours	Fever(over 38°C) Vomiting more common in children Headaches Stomach cramps Aching limbs Pediatric patients are more liable to have dehydration requiring hospitalization.	Often implicated in norovirus outbreaks are shellfish and salad ingredients. Water is the most common source of outbreaks and may include water from municipal supplies, wells, recreational lakes, swimming pools, and water stored aboard cruise ships.	Norovirus disease is also called “winter vomiting disease”
Sapovirus	Children < 5 years of age	Mild, self-limiting, nonbloody diarrhea	2–3 days	Occasionally fever and vomiting	Mainly transmitted via fecal-oral route and consumption of contaminated food (oysters, clams, salads). Outbreaks often occur in closed populations, and attack rates are high in hospitalized children, orphanages, kindergartens, schools, and in children in child-care centers.	Most cases occur during winter in temperate climates and during the rainy season in tropical climates
Rotavirus (Reoviridae family)	Children < 5 years of age. Neonatal infections are common but often mild or asymptomatic, presumably because of protection from maternal antibody or breastfeeding. First infections after 3 months of age are likely to be symptomatic; incidence peaks among children 4–23 months of age	Watery diarrheal disease	Most of the infections resolve spontaneously (4–6 days)	Fever Stomach cramps Vomiting Dehydration due to severe diarrhea is one of the major complications	The virus is usually spread by the fecal-oral route, after touching toys or things that have been contaminated by the stool of another infected child. This usually happens when children do not wash their hands after using the toilet or before eating food. The viruses can also spread by way of contaminated food and drinking water. Infected food handlers who prepare salads, sandwiches, and other foods that require no cooking can spread the disease	Winter disease in the temperate zones: incidence peaks in winter primarily in the Americas, and peaks in the autumn or spring are common in other parts of the world. In the tropics, the seasonality of such infections is less distinct. Throughout most of the world, rotavirus is present all year round