CALICI VIRUS INFECTIONS
Sharp family and community outbreaks are common and can occur in any season. Unlike rotaviruses, caliciviruses are much more common causes of gastrointestinal illness in older children and adults. This difference in age-specific predilection is perhaps reflected in serosurveys, which have shown that the prevalence of antibodies rises slowly, reaching approximately 50% by the fifth decade of life, a striking contrast to the frequent acquisi-tion of antibodies to rotaviruses early in life. Transmission is primarily fecal–oral; out-breaks have also been associated with consumption of contaminated water, uncooked shellfish, and other foods.
Both the pathogenesis and the pathology are similar to those described for rotaviruses, except that no enterotoxic features have yet been described for caliciviruses. The mucosal changes usually revert to normal within 2 weeks of onset of illness. Virus shedding in the feces generally lasts no more than 3 to 4 days.
Patients and experimentally infected volunteers respond to infection with the production of humoral antibodies, which persist indefinitely; their role in protection from reinfection, however, appears minimal. Reinfection and illness with the same serotype occur, and the role of local antibody has not been well defined. It is possible that nonimmune or genetic factors are essential for protection.
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