Does wearing a mask really make a difference? Does it matter which kind?

A case report published July 17, 2020 in the CDC’s Morbidity and Mortality Report showed the power of wearing face masks to stop the spread of the SARS-CoV-2 virus.  The report suggested wearing a face mask wasn’t just protective of others, but that it also protects the wearer.

On May 12th, a hair stylist in Springfield, Missouri developed respiratory symptoms, but kept working for 8 days until a COVID-19 test came back positive. Another stylist got sick 3 days later and worked for another 7 days before testing positive and staying home. Both stylists wore masks only when customers were present in the salon.

Six close contacts of the first stylist got COVID, but of the 139 clients exposed to either of the two symptomatic hair stylists while both the stylists and clients wore face masks, no symptomatic secondary cases were reported. Among 67 clients tested for COVID-19, all were negative. Adherence to the community’s and company’s face-covering policy likely saved the day. Robert Redfield, director of the CDC, said last week that if the American public embraced wearing face masks, the pandemic could be brought under control in less than two months.

A hypothesis among some Infectious disease researchers is that wearing a mask blocks 65-85% of viral particles. Breathing in a smaller “viral inoculum,” or smaller dose of infectious particles, correlates with having milder or even asymptomatic infection. This is likely because the immune system gets a better chance at mounting a defense. This is seen with many other viruses: it is a race between the virus replicating within the body (increasing viral load) and the immune system’s ability to kill it. Thus, breathing in less virus gives the immune system a better chance.  In areas where a high percentage of people wear masks, the number of cases may rise, but the number of deaths falls. In San Francisco, for example, with a high level of mask-wearing, the cases have risen, but the death rate has remained flat. In fact, there have been no new deaths there since June 27.

But which kind of mask is best? Researchers at Florida Atlantic University experimented with different materials and styles of non-medical masks and found that a well-fitted stitched mask made from two layers of quilting fabric was the most effective in stopping the spread of droplets from experimentally reproduced coughs and sneezes. They found that droplets from a simulated uncovered cough were able to travel more than 8 feet, with a bandana they traveled 3 feet, with a folded cotton handkerchief they traveled 1 foot, 3 inches. With a stitched cotton mask droplets only traveled 2.5 inches.

Sky Pittson, MD, July 20, 2020