Detection by Immune Electron Microscopy of 26- to 27-nm Viruslike Particles Associated with Two Family Outbreaks of Gastroenteritis

Viruslike particles 26-27 nm in size were detected by immune electron microscopy in stools of volunteers who were ill after administration of bacteria-free fecal filtrates derived from two separate family outbreaks of acute epidemic nonbacterial gastroenteritis. Fluorocarbon treatment and concentration of the filtrates were necessary to provide enough antigen to test sera by immune electron microscopy. Serum antibody responses were detected in both naturally occurring and experimentally induced cases of illness. The Montgomery County viruslike particle appeared to be related to the previously described Norwalk particle, whereas the Hawaii particle appeared to be unrelated to the Norwalk particle.