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By Gary Evans, Medical Writer
Making it all the more unfortunate that it has become politicized, there is accumulating evidence that public use of face masks could be the most effective stopgap measure against pandemic coronavirus (COVID-19).
Universal masking as a public health measure could tamp down infections overall and reduce mortality, says Monica Gandhi, MD, MPH, an infectious disease physician at the University of California San Francisco.
“I think it is going to save us from a second wave," she says. "I am profoundly hopeful of that when I look at other countries. The most effective measure, as they open up, to prevent resurgence is universal masking.”
Gandhi cites a study of a coronavirus outbreak on a cruise ship where all passengers were issued surgical masks. It was found that 81% of those testing positive for COVID-19 remained asymptomatic.
In a paper submitted for publication, Gandhi and colleagues propose an “inoculum” theory hypothesizing that masks lower the viral dose emitted and received in a setting of a universal masking. It is well-established that a mask acts as source control, protecting others from the wearer.
“But there is a second benefit that has received less attention,” Gandhi and coauthors note. “Exposure to a lower inoculum or dose of any virus (whether respiratory, gastrointestinal, or sexually transmitted) can make subsequent illness far less likely to be severe. Increasing rates of asymptomatic and mild infection with COVID-19 seen over time, in the setting of masking, supports this theory.”
In Asian countries where public mask wearing is a cultural norm, lower rates of COVID-19 mortality are being documented, the authors emphasize. “While there is some correlation between universal masking and number of COVID-19 cases, there is a near-perfect correlation between public masking and suppression of COVID-related death rates,” they conclude. “Case fatality from COVID-19 is universally low in regions with universal masking.”
There has been confused messaging and political divisiveness on this issue, with the initial rationale that mask wearing is to protect others. Gandhi argues that in a public setting, surgical masks may afford the wearer some protection by lowering the viral inoculum inhaled.
“The beginning message was that it protects others, but in a society that has not exactly been altruistic — especially in the current climate — that has not been the most effective way to convince people to wear masks,” she says. “The message needs to be that masks protect both — it protects others and it protects you as well. It makes sense that it would protect you. You can’t contract it directly through your skin — you get it into your body through your mouth or nose. Wearing a mask also protects you from touching your mouth and nose.”
Mask-wearing in public is not a cultural norm in the United States, she concedes, but neither is mass isolation of people in their homes.
“We have figured out a lot about his virus in the last few months,” she says. “We [know] that it is shed from the nose and mouth. That makes it so simple in a way — all you have to do is cover the nose and mouth.”
For more on this story, see the July 2020 issue of Hospital Infection Control & Prevention.