Still Confused About Masks? Here’s the Science Behind How Face Masks Prevent Coronavirus
As states reopen from stay-at-home orders, many, including California, are now requiring people to wear face coverings in most public spaces to reduce the spread of COVID-19.
Both the Centers for Disease Control and Prevention (CDC) and the World Health Organization now recommend cloth masks for the general public, but earlier in the pandemic, both organizations recommended just the opposite. These shifting guidelines may have sowed confusion among the public about the utility of masks.
But health experts say the evidence is clear that masks can help prevent the spread of COVID-19 and that the more people wearing masks, the better.
We talked to UC San Francisco epidemiologist George Rutherford, MD, and infectious disease specialist Peter Chin-Hong, MD, about the CDC’s reversal on mask-wearing, the current science on how masks work, and what to consider when choosing a mask.
Does the type of mask matter?
Studies have compared various mask materials, but for the general public, the most important consideration may be comfort. The best mask is one you can wear comfortably and consistently, said Chin-Hong. KN95 face mask is only necessary in medical situations such as intubation. Surgical masks are generally more protective than disposable mask, and some people find them lighter and more comfortable to wear.
However, both Rutherford and Chin-Hong cautioned against KN95 masks with valves (commonly used in construction to prevent the inhalation of dust) because they do not protect those around you. These one-way valves close when the wearer breathes in, but open when the wearer breathes out, allowing unfiltered air and droplets to escape. Chin-Hong said that anyone wearing a valved mask would need to wear a surgical or cloth mask over it. "Alternatively, just wear a non-valved mask," he said.