Viral agents of gastroenteritis: public health importance and outbreak management

Morbidity and Mortality Weekly Report, April 27, 1991

Adenovirus

Endemic disease

Adenoviruses are widely recognized causes of respiratory, ocular, and genitourinary infections. However, serotypes 40 and 41 (previously called fastidious enteric adenoviruses) primarily affect the gut, contributing to 5%-20% of hospitalizations for childhood diarrhea in developed countries 23,24). Peak incidence is among children <2 years of age, but older children and adults may be infected, with or without symptoms. Infections occur throughout the year with no clear peaks (25). Other serotypes of adenovirus, particularly 31, have also been associated with diarrhea (26).

Clinical syndrome

Incubation is between 3 and 10 days, with illness lasting -1 week, longer than for other enteric viral pathogens 23,27). Diarrhea is more prominent than vomiting or fever, and respiratory symptoms are often present. Modes of transmission

Person-to-person transmission is presumably the principal mechanism for the spread of infection. Asymptomatic shedding has been documented, but generally infectivity parallels symptomatic disease (25). Food and water have not been reported as vehicles. Outbreak characteristics

Reported outbreaks have tended to occur in hospitals or day-care settings, and all have involved children. Adult contacts were infrequently affected 28,29). immunity

Long-term immunity is thought to be acquired during childhood infection.

Calicivirus Endemic disease

A British study suggested that approximately 3% of children hospitalized for diarrhea excrete calicivirus (30), and a U.S. study found approximately the same percentage (2.9%) for children with diarrhea in day-care centers (31 ). On the basis of antibody-prevalence studies of pooled immunoglobulin and serum samples from many parts of the world, most persons appear to have been infected by age 12, and the peak acquisition takes place between 3 months and 6 years 32,33). Seasonality is unknown.

Clinical syndrome

The incubation period is 1-3 days, with illness lasting an average of 4 days. Vomiting and diarrhea are common, with upper respiratory symptoms and fever occurring less frequently. Infections in the elderly have also been documented. Modes of transmission

Person-to-person transmission is presumed to be essential for endemic disease, but contaminated shellfish, cold foods, and drinking water have been implicated as vehicles (34).

Outbreak characteristics

Of seven calicivirus outbreaks reported in the literature since 1979, all occurred in institutional settings. Four outbreaks affected children: one in an orphanage and another at a school in Japan 35,36), and one in an infant-mother hospital unit and another at a school in England 37,38). Three outbreaks involved the elderly in nursing-home settings in England and Japan (39-41 ). Attack rates ranged from 50% to 70%. No calicivirus outbreak in the United States has been reported. immunity

In the reported outbreaks, mothers of infected infants were rarely infected, suggesting that young adults retain effective immunity from earlier exposures, although the outbreaks among the elderly suggest that this immunity may wane with age.