Detection and sequencing of Norwalk-like viruses from stool samples in Japan using reverse transcription-polymerase chain reaction amplification.

Norwalk-like viruses were detected in Japan in 12% (26/209) of patients with nonbacteria and nonrotavirus gastroenteritis in an outpatient clinic of a hospital from 1991 to 1994 by reverse transcription-polymerase chain reaction. They were also present in 7% (26/378) of total samples including those from rotavirus-positive gastroenteritis patients. In addition, the viruses were recovered in samples from 15 of 17 patients which were collected during outbreaks of gastroenteritis in various places in Japan by the same method. The DNA sequence of the polymerase region from patients at the hospital (sporadic cases) showed that two subgenogroups, similar to UK1-6 in genogroup G1 and to UK1-1 in genogroup G2 (Ando et al, J Clin Microbiol, 1995, 33: 64-71) exist in Japan. The latter was more frequently found.