A new study shows that COVID-19 quickly loses its ability to infect people seconds after it becomes airborne. Researchers with the University of Bristol's Aerosol Research Center found that the virus loses about 50% of its ability to infect within ten seconds in a typical office environment.
Within 20 minutes of becoming airborne, the virus loses 90% of its ability to infect people.
"A decrease in infectivity to ∼10 % of the starting value was observable for SARS-CoV-2 over 20 minutes, with a large proportion of the loss occurring within the first 5 minutes after aerosolization," the researchers wrote in the pre-print study.
Because the virus spreads in tiny droplets expelled from the lungs, it quickly loses the ability to infect people when exposed to dry air. However, when the relative humidity is higher, the virus will keep its ability to infect people for more extended periods of time.
When they tested samples in the air with 90% humidity, which is the equivalent of a shower, they found that 52% of particles were still infectious after five minutes. However, by 20 minutes, just ten percent of the particles were still infectious.
The researchers also noted that the pH levels rapidly increase when the carbon dioxide in the environment decreases.
"People have been focused on poorly ventilated spaces and thinking about airborne transmission over meters 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," Professor Jonathan Reid, director of the University of Bristol's Aerosol Research Centre and the study's lead author, said, according to The Guardian. "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]."