According to foreign media reports, a recent study in the United Kingdom for the first time simulated the process of decay of new coronavirus particles exhaled by the human body in the air. The results show that the new crown virus loses 50% to 60% of its infectivity within the first few seconds of exposure to the air. Within 20 minutes, if the virus has not "found" the next host, it will lose 90% of its infected capacity.
The study further demonstrates the importance of social distancing and wearing masks as the "most effective" means of preventing infection. In addition, studies have shown that as virus particles leave the lungs in a relatively humid and carbon dioxide-rich environment, they quickly lose water and dry out.
Since the rate at which the virus dries out in the air and decays with the relative humidity of the surrounding air, keeping the room ventilated and dry can also have a certain anti-infection effect.
For the first time, the survival of the virus in the air was simulated, and some of the results may overturn previous conclusions
Previously, U.S. researchers have reportedly tried to assess how long the coronavirus survives in the air. In their experimental study, they used a nebulizer to produce aerosols and fed them into Goldberg drums, a high-power rotating machine, under controlled laboratory conditions, to simulate the spread of droplets in the air. The study found that virus particles could still be detected after 3 hours.
However, the aerosols induced by this experiment do not accurately reflect how the virus in aerosol particles survives in the air when the human breathes or coughs.
↑ Schematic diagram of the experimental apparatus Image source The University of Bristol research team
So researchers at the University of Bristol in the United Kingdom have developed a new device capable of producing any number of tiny, coronavirus-containing aerosol particles and gently suspending them between two electrical rings for 5 to 20 minutes. The research team strictly controlled temperature, humidity and light intensity to simulate the behavior of virus particles exhaled by the human body in the air.
"This is the first time it's really possible to simulate the aerosols produced during exhalation, what happens to them in the air." Professor Jonathan Reid, director of the Centre for Aerosol Research at the University of Bristol and leader of the study, said.
According to the study, the human body exhales high humidity bioaerosol particles. When virus particles leave the relatively humid and carbon dioxide-rich environment of the lungs and are exposed to air, they quickly lose water and dry out. The virus loses 50 to 60 percent of its infective capacity in the first few seconds of entering the air, and 90 percent of its infectivity within 20 minutes.
Loss of viral infectivity is associated with an increase in its pH. The researchers said that when virus particles leave the lungs and turn into air with lower carbon dioxide concentrations, the pH increases, which undermines the virus's ability to infect human cells. In addition, the researchers said that air temperature had no effect on the infectivity of the virus, which contradicted previous research that the new coronavirus is not easy to spread at higher temperatures.
All three of the new coronavirus variants tested by the team's experiments reportedly had the same effect, including the Alpha variant. The researchers say experiments on the Ami kerong variant will begin in the coming weeks. At present, the study has not yet been peer-reviewed.
Studies have shown that humidity is the main influencing factor, but the biggest risk of infection is distance
According to the study, the rate at which virus particles dry out varies depending on the relative humidity of the surrounding air. In many offices, for example, the environment is relatively dry, and after the virus spreads through the air for about 10 seconds, it loses about 50% of its ability to infect, and then the rate of decline is slower and more stable. In environments with high humidity, such as steam rooms or shower rooms, the decline in viral infection capacity is more slow, and half of the infectivity is lost after 5 minutes.
↑ Poorly ventilated spaces such as bars are more conducive to the spread of the virus.
Dr Stephen Griffin, associate professor of virology at the University of Leeds, stressed the importance of indoor ventilation. "In the absence of proper ventilation, if there is an infected patient, the exhaled virus particles will constantly fill the indoor space," he said. ”
Professor Reed, the leader of the study, said that the biggest risk of infection lies in distance. "People have been paying attention to poorly ventilated spaces, which really speeds up the spread of the virus. But I think the biggest risk of infection is still the distance between it and the virus. Professor Reid said. This means that if I eat with friends at a bar, the main risk may be that I will spread the virus to my friends, or that my friends will pass it on to me instead of anyone else in the house. ”
Professor Reid said social distancing and wearing a mask were the most powerful tools for preventing infection. "When you're farther away, virus particles are diluted less during airborne transmission. In addition, because the virus spends more time looking for a host, it has lost most of its ability to infect cells. ”
Red Star News reporter Wang Yalin intern reporter Ding Wen
Edited by Zhang Xun
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