Asymptomatic human calicivirus infection in a day care center.

Human caliciviruses (HCVs) are little known, recently recognized viruses associated with gastroenteritis. We identified HCV infection in an outbreak of gastroenteritis which occurred in one room of a day care center (DCC) participating in a longitudinal study of diarrhea. Utilizing an enzyme-linked immunoassay and immunosorbent electron microscopy to detect HCV, we tested specimens from all children in attendance during the period of the illness outbreak and during prior and subsequent weeks. HCV infection was documented in 14 children, 11 of whom were asymptomatic. Thirteen of the 14 HCV-infected children were 8 months of age or younger. New cases of HCV infection occurred during a 4-week period. Forty percent of children less than 1 year of age were infected with HCV during the period of investigation. Few documented HCV infections have been reported. This may be related to a high attack rate of predominantly asymptomatic infections in early life, resulting in a high prevalence of antibody to HCV by 4 years of age.