science behind wearing masks to prevent the spread of COVID-19

In the time of COVID-19, most cities, towns, and organizations around the world are not only recommending citizens to wear masks, but are requiring it. For some this has sparked a debate about whether or not this should be mandatory. So what does the science say?

SARS-CoV-2, commonly known as COVID-19 or coronavirus, is known to spread quickly from person-to-person via touch and bodily fluids, which includes spit. When a person talks, coughs, or sneezes it is extremely easy for that fluid to transfer to another person within a 6 foot radius. Their respiratory droplets are expelled into the air, and evaporate into fine particles that may linger. The mask traps these larger droplets before they can evaporate. So, wearing a mask regularly can prevent spreading at the source even when we don’t know we are sick. You would be surprised how much you spit when you talk – so one more reason to not be a close talker! (Seinfeld anyone?)

The Centers for Disease Control and Prevention (CDC) has recommended from the very onset of the virus, that all people 2 years of age and older wear a cloth face covering in public settings and when around people who don’t live in your household, especially when other social distancing measures are difficult to maintain.

A main argument to not wearing masks some have said, is that it could be dangerous for those with medical or breathing problems. The CDC recognizes that wearing cloth face coverings may not be possible in every situation or for some people. In some situations, wearing a cloth face covering may exacerbate a physical or mental health condition, lead to a medical emergency, or introduce significant safety concerns. Adaptations and alternatives should be considered whenever possible to increase the feasibility of wearing a cloth face covering or to reduce the risk of COVID-19 spreading if it is not possible to wear one. If cloth face coverings cannot be used, make sure to take other measures to reduce the risk of COVID-19 spread, including social distancing, frequent hand washing, and cleaning and disinfecting frequently touched surfaces.

So where is the proof that masks help prevent the spread?

A recent study published in Health Affairs compared the COVID-19 growth rate before and after mask mandates in 15 states and the District of Columbia. It found that mask mandates led to a slowdown in daily COVID-19 growth rate, which became more apparent over time. The first five days after a mandate, the daily growth rate slowed by 0.9 percentage-points compared to the five days prior to the mandate; at three weeks, the daily growth rate had slowed by 2 percentage-points.

Another study looked at COVID-19 deaths across 198 countries and found that those with cultural norms or government policies favoring mask-wearing had lower death rates.

Two compelling case reports also suggest that masks can prevent transmission in high-risk scenarios. In one case, a man flew from China to Toronto and subsequently tested positive for COVID-19. It was reported that he had a dry cough and wore a mask on the entirety of the flight, and all 25 people closest to him on the flight tested negative for COVID-19. In another case, in late May of this year, two hair stylists in Missouri had close contact with 140 clients while unknowingly contagious with COVID-19. However, with everyone wearing a mask, none of the clients tested positive.

The scientific world is unanimous in saying that wearing masks consistently when in public will greatly help slow the spread of COVID-19. We can do our part by wearing a cloth face covering when venturing into public.


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