Members of the family Caliciviridae (Norwalk virus and Sapporo virus) are the most prevalent cause of gastroenteritis outbreaks among infants in Japan

Norwalk virus (NV) and Sapporo virus (SV) were approved as type species of the genus Norwalk-like viruses and the genus Sapporo-like viruses, respecti vely, within the family Caliciviridae. To clarify the importance of NV and SV as causes of gastroenteritis outbreaks in infants, stool samples obtaine d from 36 outbreaks of nonbacterial gastroenteritis that occurred during 19 76-1995 in an infant home in Sapporo, Japan, were examined for diarrhea vir uses using electron microscopy, enzyme immunoassays, reverse transcriptase- polymerase chain reaction (PCR), and sequencing of the PCR products. NV and SV were associated with 15 (42%) of the 36 outbreaks and were more prevale nt than rotavirus (RV) A, which was associated with 10 (28%) of the 36 outb reaks, Our data indicate that NV and SV were the most common cause of outbr eaks of viral gastroenteritis in infants and were indeed more prevalent tha n RV-A in Sapporo. Japan, during 1976-1995.