Studies on the virus content of mouth washings in the acute phase of smallpox.

Epidemiological observations suggest that smallpox is not highly infectious in the febrile pre-eruptive period of illness. As virus is first discharged by most patients from lesions in the mouth or upper respiratory passages, mouth washings or garglings from smallpox patients in the acute stage of the disease were examined for virus. Only five specimens were obtained in the first two days of illness but no virus was recovered from them. Virus was most frequently found in specimens collected from the sixth to the ninth day of illness inclusive-a period when lesions in the mouth were breaking down and discharging virus. The results are in conformity with the view that the smallpox patient is most infective in the first few days of the eruptive phase of his illness.