Molecular epidemiology of Norwalk-like virus (NLV) outbreaks occurring in Kyushu Japan between 1988 and 1993.

In nine outbreaks that occurred in the Kyushu district between 1988 and 1993, we determined the nucleotide sequences of Norwalk-like virus (NLV) gene fragments amplified by RT-PCR and molecular-epidemiologically analyzed the NLV epidemics. It is known that the NLV strains isolated from nine outbreaks of acute gastroenteritis, were divided into five clusters consisting of two genogroups. Described by the year of outbreaks, the genogroup-1 (Norwalk-like virus group) was prevalent in 1988, 1989, and 1992, the genogroup-2 (snow mountain-like virus group) was detected in 1988, 1989, and 1993. Especially it was revealed that various strains of NLV were prevalent in the Kyushu district from 1988 to 1989. Epidemics of the Norwalk-like strain continued to be prevalent in 1992 (FP/7/92), and the strains very close to OSAP 18 continued to be prevalent in 1993 (FP/8/93, FP/9/93). Although the strains belonging to Norwalk virus (KY89) in the genogroup-1 and belonging to P1B (OSAP 18) in the genogroup-2 were detected for a prolonged period from 1988 to 1992/ 1993, the homology in these strains was very close, and this study shows that a high homogeneity was conserved in these strains. It was revealed that various strains of NLV were prevalent in the Kyushu district from 1988 to 1989.