A study by the Australian National Science Agency (CSIRO) shows that in a dark environment and at room temperature, the virus could survive for up to 28 days on smooth surfaces. However, some researchers temper these results.
As the health situation continues to deteriorate around the world, researchers continue to study Sars-CoV-2, the cause of the pandemic, with the aim to better understand it. On the transmission side, we recently learned that the coronavirus can not only be carried by droplets emitted by coughs and sneezes , but also be transmitted by the finest respiratory particles (aerosols) capable of remaining suspended in the air for several minutes.
However, are these the only two possible transmission routes? No, answers a study, inviting us to keep a close eye on what we touch.
As part of this work, researchers from the Australian National Science Agency (CSIRO) took a strain of SARS-CoV-2 and suspended it in a solution designed to mimic human mucus. The final concentration of virus in this "fake mucus" was 4.97 × 10 7 /ml, that is as much as the amount of virus present in the mucus of a COVID-19 patient with a high viral load.
Researchers then allowed the mucus to dry on surfaces of stainless steel, glass (like those in our phones), vinyl, cotton, polymer, and paper towel. three different temperatures:20°C, 30°C and 40°C and without exposure to light . They finally collected this mucus at several intervals:one hour, 1, 3, 7, 14, 21 and 28 days after inoculation.
They then discovered that at 20°C, Sars-CoV-2 can survive up to 28 days on glass, steel and polymer banknotes . This duration drops to seven days at a temperature of 30°C and 24 hours at 40°C. On the other hand, the virus survived for a shorter time on cotton, which is more porous:up to fourteen days at 20°C and less than 16 hours at 40°C.
As a reminder, a previous study had suggested that the coronavirus could survive up to three days on non-porous surfaces. In reality, the lifespan of the pathogen could therefore be significantly longer. “For context, similar experiments for influenza A showed that these viruses could survive on surfaces for 17 days, showing just how resilient SARS-CoV-2 is “, emphasizes Debbie Eagles, co-author of the study.
Questioned on the ABC channel, the director of the Center for Disease Prevention Trevor Drew nevertheless tempered these results. The researcher points out that this research was carried out with fixed levels of virus, probably corresponding to the peak of an infection and in the absence of exposure to ultraviolet light you. However, we know that this can alter the virus.
Furthermore, the amount of virus able to infect tissue culture after 28 days was still significantly reduced compared to the initial sample . However, we do not know if this quantity would be sufficient to infect a new person.
Cardiff University upper respiratory specialist Ron Eccles agrees. In particular, he reminds us that the fact of not having used real mucus in the context of this study is also a real problem, insofar as real mucus contains enzymes which would normally break the virus.
According to him, the conclusion that the virus can survive for 28 days could therefore cause "unnecessary fear in the audience. “In my opinion, infectious viruses do not persist for more than a few hours “, he told the BBC.
Still, "if indeed the precise role of surface transmission, the degree of surface contact, and the amount of virus needed for infection remains to be determine, determining how long this virus remains viable on surfaces remains critical to developing risk mitigation strategies in high contact areas “, defends Debbie Eagle.
