Air sampling to recover variola virus in the environment of a smallpox hospital.

The view is widely held that variola is highly infectious, and it was therefore thought of interest to obtain precise information on the amount of virus disseminated in the air by smallpox patients at various stages of their illness. To this end, measured samples of air in and around the smallpox wards of the Infectious Diseases Hospital, Madras, were tested for the presence of variola virus. Surprisingly, virus was recovered on one occasion only by the air sampling device used. All other tests were negative although large volumes of air were sampled in close proximity to patients at various stages of the disease. The authors consider that further observations should be made with more sensitive air sampling methods.