The new data on the effectiveness of masks against coronavirus


Even in this phase 2 of the coronavirus emergency, the use of masks is a hotly debated topic. According to new research, however, they are useful tools to contain the spread of coronavirus

(Photo: Antonio Masiello / Getty Images)

Among the main protagonists of the lockdown phase, the masks continue to be talked about even in this phase 2 of the emergency coronavirus. In fact, their role in reducing and managing to contain the spread of the new coronavirus it was widely debated, between those who praised its potential and those who, on the other hand, were immediately doubtful, diminishing their effectiveness. But now in a new and extensive review, waiting to be published in the magazine PNAS, researchers from the University of California of Los Angeles have pinned the fact that masks they represent a useful tool in reducing the spread of COVID-19.

We know that the new coronavirus is mainly transmitted through the now famous ones droplet, the saliva droplets infected that can affect those in the immediate vicinity and infect them. According to the recommendations of theWorld Health Organization (WHO), however, the masks are not used to protect themselves from infection, but rather to protect others from those who are positive for coronavirus (therefore also presymptomatic and asymptomatic). Furthermore, again according to WHO, if their use is not associated with the main measures to contain the spread of the new coronavirus, i.e. maintain the safety distance at least one meter from each other and wash regularly hands with water and soap, the masks become useless, if not harmful, as they can give a false sense of security to the wearer.

In the new study, the researchers investigated the effects of surgical masks, which hold the virus inside (filtering power on the emission source) and masks equipped with filters, i.e. those capable of blocking the virus intake (filtering power towards the outside), demonstrating how their use is an effective aid. “Most of the evidence available in the literature indicates that the use of the mask limits the transmission of the virus through the infected droplets both in the laboratory and in clinical settings, while in public it is more effective when their use is greater “, we read in the study. “A reduced transmissibility could substantially decrease the death toll and the economic impact”. As the researchers point out, the recommendation to follow is to use them masks (also those of fabric, in case the medical ones are missing) in public, in combination with hygiene, spacing and contact tracking strategies. “We recommend governments to strongly encourage the use of masks in public”continue.

Commenting on this new review was Enrico Bucci, biologist at Temple University of Philadelphia, in a long post published on Facebook, in which he underlines the importance of using masks in public. “The lesson is very clear: the masks, as we know at least since 1918 (Spanish) are an effective protection”, writes Bucci. “They are limiting of our behavior, heavy from a social point of view, perhaps not sustainable in the long run; but as long as the virus circulates, they help and how. In addition, the masks can make the bulk of the preventive work“.


The expert focuses on a graphic proposed by the researchers of the review, which you see above. “The authors consider two variables: the power of the masks to block the virus (from 0 to 100%, on the x axis) and the fraction of the population that uses the mask (on the y axis, from 0 to 100%) “. The color of the graph, continues the expert, is indicative of the value assumed by the famous parameter R (basic reproduction number indicating the potential transmissibility of an infectious disease) for each possible pair of values. In the blue zone, therefore, there are cases where R falls below 1. “A mask that filters the virus to the 60%, adopted by 80% of the population, for example, determines an R value below 1, which falls in the blue area of ​​the graph; the epidemic then dies out “, explains Bucci. “A mask with 80% of filtering power, adopted only by 10% of the population, on the other hand, falls in an area where R is greater than 2“. As the expert would like to point out, like all studies of this kind, the latter also presents some limitations, due to the extreme simplification in modeling the masks on a single parameter (the filtering power) “Which in reality is not easily controlled, because it also depends on people’s behavior (how correctly the masks are worn, their duration, etc.)”, concludes Bucci.

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