The question of whether COVID-19 can be spread through breathing has been a topic of much debate. A panel of experts from the National Academy of Sciences (NAS) recently conducted a study to answer this question. The study found that masks can reduce the transmission of coronavirus and influenza virus infections if worn by symptomatic people. The NAS panel cited the work reported in an article by Nancy Leung of the University of Hong Kong and her colleagues.
They collected respiratory droplets and aerosols from patients with respiratory diseases caused by viruses; some of the patients wore surgical masks. Masks reduced detection of coronavirus RNA in both respiratory droplets and aerosols, but only in respiratory droplets among influenza patients. The study concluded that surgical masks could prevent human coronavirus transmission and influenza virus infections if worn by symptomatic people. It is also important to note that COVID-19 can spread from asymptomatic but infected people through small aerosol droplets on exhaled breath.
Most studies on exhaled airflow have focused on coughing or sneezing, which can cause aerosols to fly long distances. For more technical information, readers can refer to Scientific and Technical Resources Related to Indoor Air and Coronavirus (COVID-19) or Key References and Publications on Indoor Air and COVID-19.