Molecular characterization of sapovirus detected in a gastroenteritis outbreak at a wedding hall

Abstract

Sapovirus (SaV) is an important pathogen of human acute gastroenteritis. A gastroenteritis outbreak occurred at a wedding hall in October 2007 in Ehime Prefecture, Japan. One hundred nine people who had either attended wedding parties or had eaten a box lunch at a conference held at the same hall complained of gastroenteritis symptoms. Among these 109 people, stool specimens from 56 patients were available for pathogen screening, and 20 (35.7%) of these specimens were positive for SaV, of whom 18 showed symptoms. The numbers of cDNA copies of the specimens ranged from 2.36 x 10(6) to 3.03 x 10(10) for symptomatic patients, and 2.19 x 10(6) and 1.18 x 10(9) per gram of stool for two asymptomatic food handlers. The incubation periods of the 18 symptomatic patients ranged from 14.5 to 99.5 hr. Identical nucleotide sequence types of SaV; that is, a single synonymous nucleotide difference (transition) or microheterogeneity, was detected in stool specimens from the symptomatic patients and the asymptomatic food handlers, with the direct nucleotide sequence of approximately 2.3 kb 3' end of the genome. Based on the phylogenetic analysis with the complete capsid nucleotide sequence, these strains were clustered into genogroup IV. This outbreak was thought to be caused by a single source, and underscores the importance of proper hygiene in the environment and/or in food-handling practices to control SaV outbreaks.