COVID-19: 4 things to know about face masks
2. How effective are masks?
The New England Journal of Medicine published the results of an experiment, where numerous droplets generated from simply saying a few words were nearly all blocked when a damp washcloth was worn over the speaker’s mouth.
“[T]his showed a decrease in the number of forward-moving droplets,” NEJM wrote.
A study published in Health Affairs last month examined the effects of state government mandates for face mask use. Researchers looked at the county-level daily growth rate of COVID-19 cases before and after the mandates in 15 states plus D.C (between March 31 and May 22).
It found “a significant decline in daily COVID-19 growth rate after mandating facial covers in public, with the effect increasing over time after signing the order.”
“Mandating face mask use in public is associated with a decline in the daily COVID-19 growth rate by 0.9, 1.1, 1.4, 1.7, and 2.0 percentage-points in 1–5, 6–10, 11–15, 16–20, and 21+ days after signing, respectively.”
Among states that require that only certain employees wear face masks (rather than all residents), results show “no evidence of declines in daily COVID-19 growth rates with the employee-only mandates.”
“The study provides direct evidence on the effectiveness of widespread community use of face masks from a natural experiment that evaluates effects of state government mandates in the US for face mask use in public on COVID-19 spread,” researchers said. “These estimates are not small and represent nearly 16–19% of the effects of other social distancing measures.”
A study in the Annals of Internal Medicine that was conducted on four participants with COVID-19 by researchers in South Korea had concluded that “neither surgical (not including N95 masks) nor cotton masks effectively filtered SARS–CoV-2 during coughs by infected patients.”
That study, published in April, was retracted in June.
