Further studies of 35--40 nm virus-like particles associated with outbreaks of acute gastroenteritis.

Virus-like particles similar in size and morphology to the Otofuke agent, which was detected first in an institutional outbreak of acute gastroenteritis at Otofuke, Hokkaido, Japan in 1978, were again observed in faeces from patients in four other outbreaks of acute gastroenteritis in Hokkaido. In each of three outbreaks in which the faeces and paired sera of patients were available, apparent sero-responses against the particles obtained in corresponding outbreaks were confirmed. Serological analysis of the particles from five separate epidemics by immune electronmicroscopy suggested that the particles from these epidemics may be related antigenically to one another. Besides the above-mentioned particles measuring 35--40 nm in diameter, 15--20-nm "empty" particles were also found in the stool specimens obtained from two of the five epidemics. In addition, serological cross reactivity between these two kinds of particles was observed. These findings provide further support for the aetiological role of the 35--40-nm particles (Otofuke agent-like particles) in acute gastroenteritis in older children and adults.