Face masks effectively limit the probability of SARS-CoV-2 transmission

• Published in: Science Vol. 372; no. 6549; pp. 1439 - 1443
• Main Authors: Cheng, Yafang, Ma, Nan, Witt, Christian, Rapp, Steffen, Wild, Philipp S, Andreae, Meinrat O, Pöschl, Ulrich, Su, Hang
• Format: Journal Article Web Resource
• Language: English
• Published: United States The American Association for the Advancement of Science 25.06.2021; American Association for the Advancement of Science
• Subjects: Abundance; Airborne infection; Coronaviruses; COVID-19; Disease transmission; Epidemiology; Expulsion; Geochem Phys; Hazardous materials; Health care facilities; Indoor environments; Infections; Masks; Pandemics; Protective equipment; Respiratory diseases; Severe acute respiratory syndrome; Severe acute respiratory syndrome coronavirus 2; Sneezing; Viral diseases; Viruses
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.abg6296

Airborne transmission by droplets and aerosols is important for the spread of viruses. Face masks are a well-established preventive measure, but their effectiveness for mitigating SARS-CoV-2 transmission is still under debate. We show that variations in mask efficacy can be explained by different regimes of virus abundance and related to population-average infection probability and reproduction number. For SARS-CoV-2, the viral load of infectious individuals can vary by orders of magnitude. We find that most environments and contacts are under conditions of low virus abundance (virus-limited) where surgical masks are effective at preventing virus spread. More advanced masks and other protective equipment are required in potentially virus-rich indoor environments including medical centers and hospitals. Masks are particularly effective in combination with other preventive measures like ventilation and distancing.