LAUSR

Background: During respiratory viral infection, face masks are thought to prevent transmission (1). Whether face masks worn by patients with coronavirus disease 2019 (COVID) prevent contamination of the environment is uncertain (2, 3). A previous study reported that surgical masks and N masks were equally e ective in preventing the dissemination of in uenza virus (4), so surgical masks might help prevent transmission of severe acute respiratory syndrome–coronavirus 2 (SARS–CoV). However, the SARS–CoVpandemic has contributed to shortages of both N and surgical masks, and cotton masks have gained interest as a substitute.