Researchers gathered patients with different types of SARS and got them for half an hour to breathe, speak and cough into a device that analysed the number of viral particles in the exhaled air. Half of the subjects were in medical masks. It turned out that masks can be effective, but not all viruses and not for all transfers. Seasonal coronavirus they worked best, although how this actually reduces the infectiousness of the patient, is unclear. Work published in the journal Nature Medicine.
One of the causes of the pandemic of the new virus SARS-CoV-2 was its infectiousness. He propagated not only in the lungs during pneumonia, but also in the upper respiratory tract, where it gets in exhaled human air. Scientists believe that coronavirus particles can be distributed not only in the form of large droplets (>5 microns), but in the form of aerosol (particles less than 5 microns). At least from the air chambers that are sick COVID-19, were able to identify a single viral RNA.
A reliable way to stop the spread of the coronavirus is considered a medical mask, but still it was not clear to what extent they are effective (including against other respiratory infections). In addition, scientists and then write about other ways of transmission — for example, through the mucous membrane of the eye — which mask to prevent not.
To find out exactly how well the mask fight off the infection, a group of researchers under the leadership of Benjamin Cowling (Benjamin Cowling) from the University of Hong Kong selected 111 patients with different respiratory infections. Among them, 54 were sick with rhinovirus, 43 of the flu, and another 17 seasonal coronavirus, a relative of SARS-CoV-2 (in total there are 114, but three people were carriers of multiple viruses at the same time). The researchers noted that symptoms in patients manifested differently in patients with influenza were more often increased temperature, and coronavirus patients often coughed. As control served the same number of healthy people.
All of the subjects at random were asked to wear or not to wear a mask, and further invited them for a half hour to breathe, to cough and talk (optional) in a special apparatus for collecting exhaled air, which is the same group of researchers has developed before. The air then condensed and measured the number of viral particles. In addition, patients collected swabs from the nose and throat, to compare if there’s anything different distribution of particles from a place of reproduction of the virus.
The authors noticed that all three viruses spread better if multiply in the nose. But the effectiveness of masks for them were different. The spread of rhinoviruses masks could not stop: and drop, and the aerosol is passed through them in the same way as without them. Against flu virus masks were effective, but only for droplet transmission. In the case of the coronavirus mask stopped both ways of transmission: drip, spray and the number of viral particles in the sample fell by several orders of magnitude.