Virus-like particle, 35 to 40 nm, associated with an institutional outbreak of acute gastroenteritis in adults.

In an outbreak of acute gastroenteritis in an institution for the mentally retarded at Otofuke, Hokkaido, Japan, virus-like particles were observed by electron microscopy in five of seven stool specimens from the patients. The particles had 10 rod-shaped and 10 round projections or capsomeres on the periphery, measured 35 to 40 nm in diameter, and had a buoyant density of 1.35 to 1.37 g/ml in cesium chloride. Attempts to culture these particles in tissue culture or in mouse brain were unsuccessful. Immune electron miscroscopy performed with the virus from the patients as antigen demonstrated significant serological responses in all patients examined. Antigenic similarity of the virus particles obtained from five patients was also confirmed by immune electron microscopy with the paired acute- and convalescent-phase sera of one of the patients. Furthermore, in immune electron micrsocopy these particles appeared to have no antigenic relationship to three candidate viruses for gastroenteritis so far reported: the Norwalk agent, the W agent, and the calicivirus-like particle. These results suggested the possibility that this agent, tentatively designated as the Otofuke agent, might be a new candidate virus for gastroenteritis.