The coronavirus can lose up to 90% of its ability to infect humans within 20 minutes of being in the air, while most of its virulence decreases in the first five minutes, according to estimates by British scientists, who made simulations of the virus' ability to survive and infect when exhaled into the air by a carrier, combined with environmental conditions, particularly humidity.
The use of a mask and the observance of distances, as well as good ventilation of spaces, help to prevent airborne infection. "The greatest risk of exposure to the virus is when a person is close to someone. When you move away, not only is the virulent spray diluted but it is also less contagious, as it loses its infectivity within minutes," said lead researcher Professor Jonathan Raine of the University of Bristol, according to the British Guardian.
Previous studies have shown that the coronavirus can be detected in air droplets even after three hours. But a new British study - which has not yet been published - concluded that very soon after the virus-containing particles are expelled from the lungs by respiration, they begin to lose moisture and, conversely, increase their pH, resulting in increased difficulty for the virus to infect human cells. How quickly the infectious particles will lose moisture and lose much of their contagiousness will largely depend on how much humidity there is in the ambient air, in other words, the higher the humidity, the longer the coronavirus can infect.
By the time the humidity had dropped below 50% in the experiments, the virus had lost about half its infectivity in just five seconds, with a further gradual loss of an additional 19% over the next five minutes. But if the humidity was at 90% (similar to that in a bathroom, for example), the reduction in infectivity was found to be slower, with at least half of the particles (52%) remaining contagious after five minutes, falling to 10% after 20 minutes. Consequently, after 20 minutes the virus was estimated to lose about 90% of its infectivity.
Apart from the humidity that played a key role, air temperature did not appear to significantly affect the contagiousness of the virus. Contrary to popular belief, virus transmission is not lower in higher temperatures, in fact, transmissibility is the same in both low and high temperatures.