Cloth and Surgical Masks Significantly Reduce Virus’ Spread by Infected People
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Compared to people infected with the original form of the virus that causes COVID-19, those with a more recent strain exhaled 43 to 100 times more of it into the air, indicating that the disease is evolving to become more airborne, according to a new University of Maryland-led study.
The researchers also found that commonly used cloth and surgical masks reduce the amount of virus that gets into the air around infected people by about half. The study comparing the original form of SARS-CoV-2 to the Alpha variant—the dominant one when experimentation was conducted—was published last week in the journal Clinical Infectious Diseases.
“Our latest study provides further evidence of the importance of airborne transmission,” said Dr. Don Milton, professor of environmental health at UMD’s School of Public Health. “We know that the Delta variant circulating now is even more contagious than the Alpha variant.”
Because research indicates successive variants keep getting better at traveling through the air, better ventilation and tight-fitting masks, in addition to vaccination, can help offset the increased risk, Milton said.
It wasn’t simply that test subjects had more virus in their bodies, researchers said; tests showed that the amount of virus in the air coming from those with Alpha variant infections was greater by a factor of 18 than could be explained by the increased amounts of virus discovered in nasal swabs and saliva.
“We already knew that virus in saliva and nasal swabs was increased in Alpha variant infections. Virus from the nose and mouth might be transmitted by sprays of large droplets up close to an infected person. But, our study shows that the virus in exhaled aerosols is increasing even more,” said doctoral student Jianyu Lai, one of the lead authors.
To test whether masks work in blocking the virus from being transmitted among people, the study measured how much SARS-CoV-2 is breathed into the air by the infected first without a mask, and then after putting on a cloth or surgical mask. The researchers found face coverings cut the amount by about 50%, but didn’t wholly stop infectious virus from getting into the air.
Assistant Clinical Professor Jennifer German, a co-author said, “The take-home messages from this paper are that the coronavirus can be in your exhaled breath (and) is getting better at being in your exhaled breath, and using a mask reduces the chance of you breathing it on others.”
A layered approach to control measures—including improved ventilation, increased filtration, UV air sanitation and tight-fitting masks, in addition to vaccination—is critical to protect people in public-facing jobs and indoor spaces, the researchers said.
The team also included researchers from the University of Maryland School of Medicine, Walter Reed Army Institute of Research, Duke-NUS Medical School and Rice University.
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