“No evidence was presented which would justify compelling persons at large to wear masks during an epidemic. The mask is designed only to afford protection against a direct spray from the mouth of the carrier of pathogenic microorganisms … Masks of improper design, made of wide-mesh gauze, which rest against the mouth and nose, become wet with saliva, soiled with the fingers, and are changed infrequently, may lead to infection rather than prevent it, especially when worn by persons who have not even a rudimentary knowledge of the modes of transmission of the causative agents of communicable diseases.”
“Epidemiological and Statistical Data, US Navy, 1918,” Reprinted from the Annual Report of the Surgeon General, US Navy, (Washington, DC: Government Printing Office, 1919) 434.
… Not so with influenza. In fact, the infection rate of staff was as high in the high-protocol wards as in the improvised hospitals. In one improvised hospital at the Navy Training Station in Great Lakes, IL., the infection rate was higher among those corpsmen and volunteers who wore masks than those who did not!Did Masks Work? — The 1918 Flu Pandemic and the Meaning of Layered Interventions – UC Berkeley Library Update