• There is no scientific evidence they are effective in reducing the risk of SARS-CoV-2 transmission
• Their use may result in those wearing the masks to relax other distancing efforts because they have a sense of protection
• We need to preserve the supply of surgical masks for at-risk healthcare workers.

Sweeping mask recommendations—as many have proposed—will not reduce SARS-CoV-2 transmission, as evidenced by the widespread practice of wearing such masks in Hubei province, China, before and during its mass COVID-19 transmission experience earlier this year. Our review of relevant studies indicates that cloth masks will be ineffective at preventing SARS-CoV-2 transmission, whether worn as source control or as PPE. 

https://www.cidrap.umn.edu/news-perspective/2020/04/commentary-masks-all-covid-19-not-based-sound-data?fbclid=IwAR0TXoXf38DqedEhZmswfBplI07fxJn31ScqU6WFnSAJo0zkABNdIxBqiec