Covid Loses Most Infection Capacity After 20 Minutes In Air: Study

Coronavirus loses most of its ability to infect shortly after being exhaled and is less likely to be contagious at longer distances, a study from the University of Bristol's Aerosol Research Centre showed.

Researchers found that the virus loses 90% of its contagion capacity 20 minutes after becoming airborne and that most of that loss happens in the first five minutes of it reaching the air, according to the study, that simulates how the virus behaves after exhaling.

With some countries opening the debate in Europe about an endemic phase to the virus, insights into the way the virus travels across the air will help guide containment measures. The results of this study, which hasn't been peer-reviewed, reinforce the notion that the virus is mainly transmitted over short distances, providing fresh support for social distancing and mask-wearing as means to curb infections.

Investigators in the U.K. focused on three of the earlier coronavirus variants, not including the most recent omicron, but said they don't expect other circulating variants to behave differently. 

"When you move further away, not only is the aerosol diluted down, there's also less infectious virus because the virus has lost infectivity [as a result of time]," Jonathan Reid, the director of the research center, said in an interview with the Guardian, which first reported the study on Tuesday. 

The findings indicate viral particles rapidly dry out after they leave the moist and carbon dioxide-rich environment of the lungs, curbing their ability to infect other people. Air humidity was found to be a determining factor in how fast these particles are deactivated, with shower rooms seeing a slower wind down than offices. 

At humidity levels below 50%, similar to the dry air found in offices, the virus lost half of its ability to spread within five seconds. When humidity rose to 90%, akin to levels in shower rooms, the virus lost infectiousness more slowly, with over half of particles still contagious after five minutes, the study showed. 

The temperature of the air, the study says, had no impact on virus infectiousness.

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