Genetic analysis of noroviruses associated with fatalities in healthcare facilities

Norovirus outbreaks occurred in 236 healthcare facilities for the elderly in Japan during the winter of 2004-2005. Three norovirus strains associated with three fatal clinical courses were isolated from geographically separate facilities and genetically analyzed along with three strains from non-fatal cases in the same season. All six isolates were classified as the GII-4 genotype. No new variant strains like those observed in Europe in 2002 and 2004 were found in fatal cases, and the three outbreaks were deemed to have been caused by genetically close conventional norovirus GII-4 strains.