Surgical face masks may be effective in preventing the transmission of seasonal coronaviruses and influenza virus from symptomatic individuals, reports a paper published in Nature Medicine. Masks were shown to significantly reduce the detection of influenza virus in respiratory droplets and seasonal coronaviruses in aerosols. Further research is needed to determine whether masks can specifically prevent the transmission of SARS-CoV-2, which is closely related to seasonal coronaviruses.
Previous research had shown that respiratory viral infections, including those caused by coronaviruses, spread between humans mostly through close contact. However, there is no direct evidence of how influenza and coronaviruses spread between humans who are in close proximity – whether by direct contact, large respiratory droplets, or through breathing another person’s exhaled breath. Respiratory viruses can also survive in the environment and potentially spread through indirect contact. Larger respiratory droplets, which fall near the source, as well as aerosols of smaller fine particles can both contain virus and cause short-range transmission. In addition, aerosols can remain in the air for longer and potentially transmit infection over longer distances, particularly if they are generated at higher concentration or if there is little ventilation.
Non-pharmaceutical measures, such as social distancing, handwashing, ventilation, and face masks, could be important measures to prevent viral transmission. Although the use of face masks has been suggested as a strategy to slow down the transmission of influenza virus, little is known about the relative importance of this strategy in the transmission of other respiratory viruses, including seasonal coronaviruses.
Nancy Leung and colleagues recruited 246 people with suspected respiratory viral infections to breathe into a machine—the Gesundheit II—to compare the relative amount of virus in exhaled breath with or without a face mask. The authors found that in 111 people whose infections by either coronavirus, influenza virus or rhinovirus were confirmed, masks reduced detectable virus in respiratory droplets and aerosols for seasonal coronaviruses, and in respiratory droplets for influenza virus. In contrast, masks did not reduce the emission of rhinoviruses.
SARS-CoV-2 and seasonal coronaviruses are closely related and may be of similar particle size. Therefore, the authors suggest that the ability of surgical masks to reduce seasonal coronavirus in respiratory droplets and aerosols implies that such masks can contribute to slowing the spread of SARS-CoV-2 when worn by people infected with the virus.
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