Population-wide use of facemasks could effectively control the coronavirus pandemic by substantially reducing the chances that an infected wearer will pass along his viruses to another person, according to a new study in the journal Proceedings of the Royal Society A.
A team of British researchers reached this conclusion using computer modeling to evaluate several plausible scenarios of how wearing facemasks could affect epidemic trends. "Our approach is to accept that, with a new disease, it is impossible to get accurate experimental evidence for potential control interventions," they argue, "but that this problem can be approached by using mathematical modeling tools to provide a framework to aid rational decision-making."
The researchers take into account such variables as how infectious the coronavirus is, the proportion of the population that wears masks, and how effective masks are at containing exhaled and excluding inhaled virus-laden aerosol droplets. They also analyze how wearing facemasks during lockdowns affect epidemic trends.
In one scenario, the researchers find that the spread of the virus can be dramatically lowered and the epidemic controlled if everybody routinely wore facemasks in public that were only 50 percent effective. Universal masking pushes the basic reproduction or 'R' number—that is the number of people an infected individual passes the virus onto—to below 1.0, which is the level required for the pandemic to slow. It turns out that many homemade masks are even more effective than that. In fact, an earlier study reports that often they are nearly as efficient as standard surgical masks at blocking respiratory droplets.
"In all modeling scenarios, routine facemask use by 50 percent or more of the population reduced COVID-19 spread to an R less than 1.0, flattening future disease waves and allowing less-stringent lockdowns," notes the press release accompanying the study. The study also found that people wearing masks whenever they are in public is twice as effective at reducing 'R' than if they wait to don masks only after symptoms appear.
As the pandemic was taking off my Reason colleague Jacob Sullum pointed out that the public received a lot of contradictory advice about mask-wearing. The new study bolsters the case for the routine use of masks in public.
The study authors acknowledge that there may some cultural reluctance to wear facemasks in Western societies because it may be taken as implying that the wearer considers others as a threat. In fact, the researchers point out to the contrary that using a mask more effectually protects others from the wearer's microbes. "My facemask protects you, your facemask protects me," is the apt slogan that the researchers use to summarize the epidemiological benefits of wearing masks.
The researchers also suggest that mask-wearing would also offer another benefit by reinforcing the message that it is necessary to keep to a safe distance from one another. As it happens, a new study by an Italian researcher reported that that is exactly what happens. He rigged both maskless and masked folks with proximity sensors and measured more than 12,000 encounters with other people on sidewalks and in stores to find out how they reacted to people wearing masks. The result is that people did not consistently maintain social distancing with the maskless but did with mask wearers.
In the press release, lead author Cambridge University epidemiological modeler Richard Stutt concluded, "If widespread facemask use by the public is combined with physical distancing and some lockdown, it may offer an acceptable way of managing the pandemic and re-opening economic activity long before there is a working vaccine."