By Pat Staszak, PT
This is the 3rd article in what turns out to be a series of blog posts about the use and efficacy of wearing masks to control the Coronavirus. Last month we highlighted the CDC’s recent recommendation that we all wear masks, and we reviewed current evidence that shows that masks do work to control the spread of COVID-19.
This month we are again sharing information from two new studies about masks: Why they work and which type of mask is best at filtering respiratory droplets. Sometimes if we have a better understanding of how something works, we are more likely to believe in it. So it is helpful that recent studies have identified likely mechanisms for the transmission of COVID-19 that show why masks work to protect us from the virus.
Last Friday, The New York Times reported on a research team at Harvard’s T.H. Chan School of Public Health who studied the outbreak on the Diamond Princess that occurred in January 2020. In this superspreader event, one infected person on the ship passed the virus to 700 out of 3,711 others on the ship. The researchers used computer models to analyze how the virus passed through the ship. Although not yet peer-reviewed, the study confirmed what many scientists have thought for months; that the virus can spread through tiny droplets light enough to linger in the air. These microscopic droplets, also called aerosols, can float in the air for several minutes or longer. When we breathe, these droplets can be embedded in the mucus membranes of our nose or mouth.
This study supports the idea that good ventilation, preferably with a system that pulls air from the outside to replace the air indoors, is another tool we have to control the Coronavirus. It also strengthens the argument that we should all wear masks, especially while indoors. Maintaining 6 feet apart helps avoid large respiratory droplets, but it won’t protect us from these small particles that hover in the air.
To stay protected it also matters what type of mask is worn. In a simple experiment at Duke University, researchers measured the amount of respiratory droplets expelled as the subject spoke while wearing different types of face coverings. They used a low-cost optical laser, lens, and cell phone camera to measure the number of droplets expelled.
They found that not all masks are created equal. As expected, N95’s performed the best, with surgical masks and neoprene masks doing the next best job to block the respiratory particles. What was most surprising to researchers is that neck fleeces (gaiters) are worse than wearing nothing at all! Bandanas were the next least effective. So to protect yourself and others, we should not wear a neck gaiter or a bandana! They also noted that valved masks protect the wearer very well, but since air escapes through the valve while exhaling, these types of masks do not protect others.
With every week that passes, more evidence supports mask wearing to control the Coronavirus. Recent studies give us a better understanding of how they work and which masks work the best. We hope you find this information valuable, and more importantly, that it persuades you to wear high quality masks while indoors or when you are unable to social distance outside. Because of this recent research, at APT we ask all patients to avoid wearing neck fleeces (gaitors) and bandanas since they do not adequately protect against the coronavirus.