The coronavirus loses about 50 percent of its ability to infect about 10 seconds after it becomes airborne in a typical office environment, according to a new study about how the deadly bug survives in exhaled air.
“People have been focused on poorly ventilated spaces and thinking about airborne transmission over meters or across a room,” said Prof. Jonathan Reid, director of the University of Bristol’s Aerosol Research Centre, the Guardian reported.
“I’m not saying that doesn’t happen, but I think still, the greatest risk of exposure is when you’re close to someone,” said Reid, the lead author of the study, which has not yet been peer-reviewed.
“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),” he added.
The UK university researchers’ findings highlight the impact of short-range transmission — and stress the importance of physical distancing and masking up as the best way to avoid infection.
While still worthwhile, ventilation was deemed to be less effective, the news outlet reported.
The study determined that viral particles quickly lose moisture and dry out after they are expelled from the lungs. The particles’ pH also rises rapidly when the carbon dioxide in their environment drops, the news outlet reported.
The relative humidity of the surrounding air affects how fast the particles dry out.
When under 50 percent, such as the relatively dry air in an office, the virus had become half as infectious within 10 seconds. But at 90 percent humidity, 52 percent of particles remained infectious after five minutes, dropping to about 10 percent after 20 minutes.
Air temperature also did not affect the infectivity, contradicting the widely held belief that transmission is lower during warm weather.
“It means that if I’m meeting friends for lunch in a pub today, the primary [risk] is likely to be me transmitting it to my friends, or my friends transmitting it to me, rather than it being transmitted from someone on the other side of the room,” Reid said.
The British researchers generated minuscule particles that floated between two electric rings between five seconds and 20 minutes as the temperature, humidity and surrounding UV light intensity were tightly controlled, the Guardian said.
“This is the first time anyone has been able to actually simulate what happens to the aerosol during the exhalation process,” Reid said.
The experts noted the inaccuracy of experiments conducted by US researchers, who found that infectious virus could still be detected after three hours.
The Bristol team said the American scientists conducted their studies by spraying virus into sealed, rotating drums that do not allow them to recreate what happens when people cough or breathe.