A new study that claims to be the first of its kind has demonstrated that Covid-19 loses 90 percent of its ability to jump from one person to another within 20 minutes of being exhaled, with most of the drop in infectiousness occurring in the first five minutes.
The study was conducted at the University of Bristol in the United Kingdom, and used an ingenious set-up that researchers claim comes close to replicating what actually happens when people exhale aerosols that contain Covid-19 particles. Previous studies assessing airborne transmission used a different method called Goldberg drums which rotate and keep the droplets airborne, when in real life, that would be unlikely to occur due to a variety of reasons.
According to Prof. Jonathan Reid, director of Bristol University’s Aerosol Research Centre and the lead author of the study, his team allowed for the effects of temperature, humidity, and UV light intensity when investigating the behavior of the virus-containing particles.
“This is the first time anyone has been able to actually simulate what happens to the aerosol during the exhalation process,” he told The Guardian. “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. When you move further away, not only is the aerosol diluted, there’s also less infectious virus because the virus has lost infectivity [as time passes].”
The results of the study also suggest that leaving the moist, carbon dioxide-rich state of the lungs and drying out in the air greatly reduces the virus’ ability to infect others. As such, in more humid conditions, the likelihood of being infected is greater. Temperature, however, was not found to affect contagion rates, contrary to the researchers’ expectations.
The findings support what epidemiologists have been observing in real life conditions, said Dr. Julian Tang, a clinical virologist at the University of Leicester, stressing the importance of good ventilation when meeting people in enclosed spaces.