One More Reason to Wear a Mask: You’ll Get Less Sick From COVID-19
As more and more states promote face masks as a way to control the spread of COVID-19, the top-line message has been: wear a mask to protect others. While it’s true that most face masks are more effective in preventing you from launching droplets into the air than breathing in already dispersed droplets – that doesn’t mean masks offer no protection to the wearer.
It’s likely that face masks, by blocking even some of the virus-carrying droplets you inhale, can reduce your risk of falling seriously ill from COVID-19, according to Monica Gandhi, MD, an infectious disease specialist at UC San Francisco.
“The more virus you get into your body, the more sick you are likely to get,” she said.
In the latest wave of infections in the U.S., the wider use of masks may be one factor for the lower death rates – along with more testing, younger patients and better treatments – said Gandhi. A greater proportion of these new cases have been mild or asymptomatic, though more data is needed to see if they track geographically with higher rates of mask-wearing.
Worldwide, epidemiological patterns seem to provide a clue. In countries where mask wearing was already commonplace, such as Japan, South Korea, and Singapore, and in countries where mask wearing was quickly embraced, such as the Czech Republic, rates of severe illness and death have remained low, even with new cases. Countries with uneven rates of mask-wearing, like the United States, have fared more poorly.
These epidemiological observations are among the evidence that Gandhi and colleagues cite in a forthcoming paper in the Journal of General Internal Medicine, in which they propose that masks can lead to milder or asymptomatic infections by cutting down on the dose of virus people take in.
“Masks can prevent infection altogether, as was seen in healthcare workers when we moved to universal masking. We are also saying that masks, which filter out a majority of viral particles, can lead to a less severe infection if you do get one,” said Gandhi. “If you get infected, but have no symptoms – that’s the best way you can ever get a virus.”
NOT A NEW IDEA
COVID-19 is caused by an RNA virus dubbed SARS-CoV-2. The idea that viral dose, also known as viral inoculum, determines the degree of illness is not new, said Gandhi. Descriptions of a dose-mortality curve – how much of a virus is needed to cause death in an animal – were first published in 1938. And after all, the earliest vaccines, which were documented in 16th century China, involved exposing someone to a small amount of smallpox virus to induce mild illness and subsequent immunity.
Researchers have studied dose dependency experimentally with other viral infections, like the flu. In a study with healthy human volunteers, those who received a higher dose of the influenza A virus developed more severe symptoms.
Because the new coronavirus is potentially lethal, experiments on masking and disease severity have been necessarily limited to animals. In a hamster study, a surgical mask partition between the cages of infected and uninfected hamsters significantly cut COVID-19 transmission. Fewer hamsters caught the virus and those that did showed milder symptoms.
