“We Should All Wear Masks”

“…Currently, the U.S. Centers for Disease Control and Prevention recommends that everyone wears a mask – as do the governments covering 90% of the world’s population – but, so far, only 12 states in the U.S. require it. In the majority of the remaining states, the CDC recommendation has not been enough: Most people do not currently wear masks. However, things are changing fast. Every week more and more jurisdictions require mask use in public...

“Researchers from the National Institutes of Health used lasers to illuminate and count how many droplets of saliva were flung into the air by a person talking with and without a face mask. The paper was only recently published officially, but I saw a YouTube video showing the experiment in early March. The results are shockingly obvious in the video. When the researcher used a simple cloth face cover, nearly all the droplets were blocked.

“This evidence is only relevant if COVID-19 is transmitted by droplets from a person’s mouth. It is. There are many documented super-spreading cases connected with activities – like singing in enclosed spaces – that create a lot of droplets.

“The light-scattering experiment cannot see ‘micro-droplets’ that are smaller than 5 microns and could contain some viral particles. But experts don’t think that these are responsible for much COVID-19 transmission.

“Another recent study showed that unfitted surgical masks were 100% effective in blocking seasonal coronavirus in droplets ejected during breathing.

“If only people with symptoms infected others, then only people with symptoms would need to wear masks. But experts have shown that people without symptoms pose a risk of infecting others. 

“In fact, four recent studies show that nearly half of patients are infected by people who do not themselves have symptoms.

“This evidence seems, to me, clear and simple: COVID-19 is spread by droplets. We can see directly that a piece of cloth blocks those droplets and the virus those droplets contain. People without symptoms who don’t even know they are sick are responsible for around half of the transmission of the virus…

“There are numerous studies that suggest if 80% of people wear a mask in public, then COVID-19 transmission could be halted. Until a vaccine or a cure for COVID-19 is discovered, cloth face masks might be the most important tool we currently have to fight the pandemic.

“Given all of the laboratory and epidemiological evidence, the low cost of wearing masks – which can be made at home with no tools – and the potential to slow COVID-19 transmission with widescale use, policymakers should ensure that everyone wears a mask in public” (The Conversation).

Jeremy Howard, Distinguished Research Scientist, University of San Francisco