“Coronavirus, the mask can decrease infections but pay attention to exposure time and viral load”

Mandatory throughout Italy outdoors and indoors, with few exceptions. The mask is becoming a sort of “natural appendix”, so much so that sometimes if we don’t wear it we have the feeling that something is missing. Sometimes, however, it can be limiting or annoying. In recent months we have wondered which masks are more protective, if wearing them for a long time can cause damage to health, if they are bad for children. Let’s try to clarify some points with Carlo Federico Perno, virologist, director of the Microbiology Unit at the Bambino Ges pediatric hospital in Rome.

Professor, could the increase in infections we are witnessing be slowed down if we all wear masks?
The crux of the matter is how it is worn. Several scientific studies show that the coronavirus essentially resides in the nose, where there is the maximum expression of the receptor to which it binds. So the mask is totally useless if it does not perfectly cover the nose, as well as the mouth.

Do FFP2 masks protect more than surgical masks?

Carlo Federico Perno

Given that total protection does not exist, the FFP2 has a greater protective and filtering capacity than the surgical mask, but the latter, if worn correctly, protects sufficiently by blocking the aerosol and the droplets that carry the virus. As long as you consider two variables: the exposure time and the viral load of the infected individual with whom I eventually come into contact. If I am in a closed room with a Sars-CoV-2 positive person and there is no frequent air exchange, over time the air becomes impregnated with viruses and therefore also my mask. The “sponge effect” occurs: the mask retains the virus for a while (as a sponge does with water), but if the amount of pathogen is very high, the filtering capacity is lost. For this reason, the exchange of air in closed environments is very important, opening the windows for a few minutes every half hour (maximum every hour) or leaving a chink constantly open. But the second factor is also fundamental: the viral load of the positive subject. If low, the risk of contagion is very limited, even with the passage of time and in the absence of ideal ventilation. If the charge is high, the chances of contracting the infection also increase exponentially.

Do FFP3 masks offer any advantages?
No, they are not suitable for the general population.

And those of cloth?
If the fabric has a thick texture they can protect quite effectively, but they are not optimal.

Does the disposable mask need to be changed often?
Under normal conditions, especially outdoors, it is sufficient to replace it every day, or even less if you use it for a short time and it stays clean.

How long can the virus resist in the environment, remaining intact and able to infect?
We do not know exactly: it is assumed more than half an hour and less than 5-6 hours.

Is it possible to establish with a simple swab if an infected person has a low, medium or high viral load?
It can be done in all the most advanced laboratories of the Microbiology departments: in Italy there are many. Moreover, the measurement does not lengthen the examination time, nor does it have significant costs, since it is possible to have an idea of ​​the viral load (low, medium, high) already from the simple and routine molecular test. They are used for specific machinery. Today in Italy we have two types of tests: molecular (classic) and antigenic (rapid). Both are done on material collected with the nasopharyngeal swab. We are awaiting salivary tests: these too will be molecular or antigenic. Viral load can be measured on molecular swabs, of both types. Let’s consider that the quantity of Sars-CoV-2 present in subjects is enormously variable: it can range from 100 viral particles up to 100 million. The viral load explains the different infectivity of people and also the different evolution of the disease.

At which stages of the infection is the viral load highest?
It begins to rise from day zero of the infection (so already during the incubation, which can last up to 14 days, ed) and maximum when the first symptoms appear. Then it tends to decline slowly, because the virus kills the target cells, in the epithelium of the nose and the entire respiratory system, and therefore can no longer replicate.

Are there any risks associated with prolonged use of the mask?
The “side effect” of the mask is to reduce the amount of oxygen we inhale and to increase the amount of carbon dioxide we exhale. No problem when you are at rest, while if you make efforts (such as playing sports or climbing stairs) the decrease in oxygen can be harmful to the heart: this is especially true for the elderly, heart patients and the obese.

October 9, 2020 (change October 9, 2020 | 16:19)



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