Airborne transmission is the primary route for the person-to-person spread of the virus that causes COVID-19. Infected individuals disperse virus-bearing liquid particles when speaking normally, coughing, or sneezing.2,3 Face masks prevent airborne transmission by blocking dispersion of these particles.
Between 30 and 60 percent of those who have COVID-19 are either asymptomatic or pre-symptomatic. If symptoms appear, they are usually manifest within five to six days after exposure; however, symptoms can appear as long as 13 days later.4 Universal masking helps protect others during the time that infected individuals are asymptomatic and might otherwise unknowingly infect others.
Masks do not replace other effective measures to curtail COVID-19 transmission (e.g., physical distancing, frequent hand washing, monitoring for symptoms, quarantine after known exposure, and isolation after infection is suspected or confirmed). Spread is more likely when people are in close contact with one another (i.e., within about 6 feet).
By wearing masks in public, lives may be saved. Researchers from the Institute for Health Metrics and Evaluation (HME) at the University of Washington used statistical modeling to predict the total number of deaths from COVID-19 in the United States through October 1. Without the use of masks, deaths would exceed 179,000. However, if 95 percent of our population wore masks, deaths would total about 146,000.5 Masking could save 33,000 lives in just 3 months. According to the HME, wearing masks can reduce the transmission risk of COVID-19 by as much as 50 percent.5
ASA and APSF represent physicians and other health care professionals who safely wear masks on the job every day without significant health effects. Concerns about mask-related hypoxia, hypercarbia, and infection are unfounded.
In addition to protecting others, masks may also protect wearers by filtering out virus-bearing liquid particles before they are inhaled. Cover the face and mouth, fitting the mask as closely as possible to the face. Do not remove a mask when talking, coughing, or sneezing.
Spread may also occur indirectly when wearers touch a mask and then touch their eyes, nose, or mouth. This can be avoided by cleaning hands with soap and water or an alcohol-based hand sanitizer before donning a mask and after removing it. Discard disposable masks when soiled and avoid touching the front of the mask when removing it.
- Zhang R, Li Y, Zhang AL, Wang Y, Molina MJ. Identifying airborne transmission as the dominant route for the spread of COVID-19. Proceedings of the National Academy of Sciences (2020). https://doi.org/10.1073/pnas.2009637117
- Rothe C, Schunk M, Sothmann P, et al. Transmission of 2019-nCoV Infection from an Asymptomatic Contact in Germany. The New England journal of medicine. 2020;382(10):970-971.