The facts on SARS-Cov-2 are getting a little more accurate every day. The transmission routes and survival time of the coronavirus, depending on the type of surface, are being confirmed as more studies are conducted.
The coronavirus that causes the Covid-19 pandemic can survive up to 28 days in a cool, dark environment on surfaces such as telephones and banknotes, according to a study by the Australian National Science Agency (Csiro). Investigators at Csiro’s Disease Prevention Department found that the warmer the temperature, the lower the survival rate of SARS-CoV-2, the agency announced.
They found that SARS-Cov-2 is “extremely resistant” at 20 degrees temperatures on smooth surfaces, such as telephone screens. It can survive for 28 days on glass, steel, and polymer. At 30 degrees this survival rate drops to 7 days, and at 40 degrees to 24 hours.
On porous surfaces like cotton, the virus has survived less, up to 14 days at the lowest temperature, and less than 16 hours at the highest temperature. Compared to previous studies, which showed that the coronavirus can survive up to four days on non-porous surfaces, this is “significantly longer” according to the Journal of Medical Virology.
Significantly longer than first thought
Trevor Drew, director of the Australian Center for Disease Control, said the study involved drying samples of the virus on various materials before testing them with an “extremely sensitive” method. They found traces of a live virus that could infect cell cultures.
But that doesn’t mean that this amount of virus can infect anyone,” he told public television ABC. However, if a person were “careless with these materials and then licked their hands or touched their eyes or nose, they could be infected more than two weeks after the contamination,” he said.
Mr. Drew expressed reservations, particularly because this study was conducted at fixed virus concentrations, which are likely to correspond to the peak of infection, and in the absence of exposure to ultraviolet light, which can rapidly alter the virus. The humidity was maintained at 50%, according to the study, because the increase in humidity is also harmful to the virus.
According to Csiro, the virus propagates mainly through the air, but more research is needed to better understand how it is transmitted through surfaces. Drew said the main message is that “infected people are much more infectious than surfaces”.
“But it can help explain why sometimes the epidemic returns even if a country is considered virus-free, even when there are no longer infectious people,” he suggested.