Masks
Can surgical masks really decrease the amount of virus in the exhale?
Over the course of this epidemic, masks have become almost a commodity. What is their real role in containing this pandemic. Do they really have the ability to reduce the transmissibility of the virus? Two groups of researchers have asked themselves this question: in the first one there are researchers from Hong Kong and the United States who have evaluated "in the field" the real effectiveness of these so-called "surgical masks" for infected patients; while in the last one, researchers from Germany and the United States have evaluated the effectiveness of these masks in filtering droplets of saliva from professional singers.
Studies
Specifically, with regard to 2 studies both published in Nature Medicine, the authors of the first evaluated the presence of viruses in saliva droplets of various sizes released into the air by patients suffering from various respiratory diseases of viral origin; the authors of the second evaluated saliva droplets released by professional singers, all non-smokers and patients of respiratory diseases.
The first study
Among the viruses considered in the first study, there were also coronaviruses preceding COVID-19, which also cause respiratory symptoms, but less severe. The authors of this work evaluated how the quantity of viral particles emitted changed if the patient wore a mask or not. A total of 246 patients were studied, including 124 patients who wore a mask and 122 who did not. It should be noted that, in order to get as close as possible to a real situation, those who wore the mask were asked to wear it independently precisely to take into account the possibility of incorrect positioning. A very common variable in real life.
The second study
In the second study, 10 professional singers (5 males and 5 females) performed a part of the Ode of Joy twice, once with the mask and once without. 3 Sony HDC 1700R full HD cameras record 3 sides: front, side, and top. In particular, to ensure that the saliva droplets are visible, there is a laser light placed that irradiates the mentioned droplets.
The results obtained showed differences in effectiveness depending on the virus considered. In particular, with regard to coronaviruses (not those of the pandemic), the study showed a particular effectiveness in limiting their emission in patients who wore a mask. Those who wore the mask did not emit the virus in either the largest or the smallest droplets, i.e., aerosols. On the contrary, a much lower effect was found for influenza viruses and other viruses responsible for the common cold (the so-called rhinoviruses). In particular, these viruses were also found in the aerosols of those who wore masks.
The results of the second study
Also in the second study the results showed the so-called aerosol clouds differently distributed: in the case that the singer wears the mask, the aerosol cloud is mainly concentrated near the singer's ears; in the case that the singer sings without the mask, the cloud goes in the singer's forehead.
Overall, therefore, the first study described reaffirms the potential importance of wearing a mask to limit transmissions. In the second study, however, surgical masks can significantly deflect aerosol trends. We can confirm that surgical masks are able to protect third parties, as they significantly deflect aerosol patterns. If we wanted to reduce the amount of these aerosols to a minimum, we would have to wear anti-virus masks, e.g. FFP2, FFP3 (both classified as PPE).
In our opinion, although both studies reiterate the potential importance of wearing the surgical mask (the first because the effectiveness of not wearing the surgical mask correctly is low, the second because in any case, there are aerosols that pass through the surgical mask), it is always better to wear it and we must wear it correctly, because it deflects aerosols in the exhalation, which could also contain viruses. However, wearing the surgical mask correctly is not enough, it is also necessary to maintain a safety distance of at least 1.5 meters.
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