Pattern of shedding of the Norwalk particle in stools during experimentally induced gastroenteritis in volunteers as determined by immune electron microscopy

Abstract

In 1968, an outbreak of acute, infectious, nonbacterial gastroenteritis occurred in Norwalk, Ohio. A filtrate was prepared from a rectal swab specimen of an adult who developed a secondary case of gastroenteritis during that outbreak. This filtrate induced gastroenteritis when administered orally to 23 adult volunteers. In 11 of them the Norwalk virus like particle was visualized by immune electron microscopy in at least one stool specimen obtained during the acute phase of the disease. Examination of multiple stool specimens obtained during the course of illness in these 11 volunteers revealed maximal concentration of virus like particles at the onset of illness and shortly thereafter; in no case was the Norwalk particle visualized in stools obtained before the onset of illness. This finding further suggests that the Norwalk particle was the etiological agent of the Norwalk gastroenteritis outbreak. The limit of reliability of the immune electron microscopy assay system for particle counting was examined.