Abstract
Summary
Acute infectious nonbacterial gastroenteritis was induced in adult volunteers through three serial passages by oral administration of bacteria-free stool filtrates. This suggested that a replicating agent of subbacterial size was responsible for the observed disease. The biophysical properties of the agent, as assayed in volunteers, were consistent with those of a small virus, most closely related to the parvovirus group among known animal viruses. The agent appeared to have a diameter less than 66 nm and likely less than 36 nm. It appeared to lack a lipid containing envelope and was acid stable. It was stable to heating at 60° for 30 min. The agent appeared to be relatively host specific for man and conferred at least short-term immunity. Because of the high frequency of disease induced in unselected volunteers, widespread natural immunity to this agent may be absent or perhaps incomplete. Preliminary evidence suggested that the Norwalk agent replicated in an in vitro system, human fetal intestinal organ culture.
We gratefully acknowledge the cooperation of the volunteers and staff at the Maryland State House of Correction. We also thank Drs. David Fedson and Sheldon Wolff of the Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, for their help with the study, Dr. Samuel Formal of the Walter Reed Army Institute of Medical Research for performing enterotoxin assays and monkey inoculations, and Dr. Robert Purcell of the Laboratory of Infectious Diseases for performing Australia antigen determinations.
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