COVID-19 becomes 90% less contagious within 20 minutes in air, study reveals

COVID-19 becomes 90% less contagious within 20 minutes of going airborne and loses most of its potential to infect during the first five minutes, according to a pioneering new study that looks at how the fatal infection survives in exhaled air. Researchers said the findings of a study released by the University of Bristol's Aerosol Research Centre emphasise the necessity of using face masks and keeping a social distance to prevent the transmission of COVID-19.

The study, which has not yet been peer-reviewed, is the first of its type to replicate how coronavirus moves in the air after being exhaled. The researchers created an equipment to generate virus-containing particles and enabled them to float between two electric rings for anything between five seconds and 20 minutes in a closely regulated environment to replicate what happens to the virus when it gets airborne.

The Guardian reported, citing director of the University of Bristol’s Aerosol Research Centre and the study’s lead author, Prof Jonathan Reid, as saying, “People have been focused on poorly ventilated spaces and thinking about airborne transmission over metres or across a room. I’m not saying that doesn’t happen, but I think still the greatest risk of exposure is when you’re close to someone."

He added, as you get further away, not only is the aerosol diluted, but there is also less infectious virus since the virus has lost its infectivity [due to time]. According to the research, as virus particles leave the lungs, they shed a lot of water, and the reduced levels of carbon dioxide in the air cause a rapid rise in pH. According to the research paper, it has an impact on the virus's ability to infect human cells.

Air temperature has no effect on virus infectivity

In a typical office setting, where the surrounding humidity is typically less than 50%, the virus became half as infectious in under five seconds, after which the loss of infectivity got slower and more constant, with a further 19% loss over the next five minutes. In contrast, the drop is substantially slower in a more humid environment, such as a steam room or shower. The researchers discovered, however, the temperature of the air, on the other hand, had no effect on viral infectivity, contrary to popular opinion that viral transmission is reduced at high temperatures.

The findings highlight the importance of short-range COVID-19 transmission, with physical separation and mask use likely to be the most effective methods of infection prevention. While ventilation is still beneficial, it is likely to have a reduced benefit. The University of Bristol researchers devised a device that allowed them to create any number of microscopic virus-containing particles and gently hover them between two electric rings for anything from five seconds to twenty minutes. It also allowed the researchers to have complete control over the temperature, humidity, and UV light intensity in their environment.