The variants of SARS-CoV-2 are getting better at travelling through the air, and people must wear tight-fitting masks and ensure better ventilation, in addition to getting vaccinated, to help stop spread of the virus that causes Covid-19, according to a study.
The team led by researchers at the University of Maryland in the US found that people infected with SARS-CoV-2 exhale infectious virus in their breath, and those infected with the Alpha variant put 43 to 100 times more virus into the air than people infected with the original strains of the virus.
The study, published in the journal Clinical Infectious Diseases, also found that loose-fitting cloth and surgical masks reduced the amount of virus that gets into the air around infected people by about half.
"Our latest study provides further evidence of the importance of airborne transmission," said Don Milton, professor at the University of Maryland School of Public Health.
"We know that the Delta variant circulating now is even more contagious than the Alpha variant. Our research indicates that the variants just keep getting better at travelling through the air, so we must provide better ventilation and wear tight-fitting masks, in addition to vaccination, to help stop spread of the virus," Milton said.
The researchers noted that the amount of virus in the air coming from Alpha variant infections was much more -- 18-times more -- than could be explained by the increased amounts of virus in nasal swabs and saliva.
"We already knew that virus in saliva and nasal swabs was increased in Alpha variant infections," said doctoral student Jianyu Lai, one of the lead authors of the study.
"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," Lai said.
The researchers said these major increases in airborne virus from Alpha infections occurred before the Delta variant arrived and indicate that the virus is evolving to be better at travelling through the air.
To test whether face masks work in blocking the virus from being transmitted among people, the study measured how much SARS-CoV-2 is breathed into the air and tested how much less virus people sick with Covid-19 exhaled into the air after putting on a cloth or surgical mask.
Face coverings significantly reduced virus-laden particles in the air around the person with Covid-19, cutting the amount by about 50 per cent, the researchers found.
However, the loose-fitting cloth and surgical masks didn't stop infectious virus from getting into the air, they said.
"The take-home messages from this paper are that the coronavirus can be in your exhaled breath, is getting better at being in your exhaled breath, and using a mask reduces the chance of you breathing it on others," Jennifer German, a co-author of the study said.
"This means that 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," German added.
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