How often coronaviruses are transmitted by touching contaminated surfaces has yet to be fully determined.
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It is assumed that the transmission of coronaviruses takes place predominantly through prolonged and close contact from person to person. For this reason, masking, social distancing, and hand washing are critical to preventing infection. But since the beginning ofScientists have also tried to understand how SARS-CoV-2, the virus that causes COVID-19, can survive and spread through .
New research by scientists at CSIRO, Australia's national science agency, suggests that SARS-CoV-2 can linger on non-porous surfaces longer than expected. The study, published Monday in the Virology Journal, was conducted under controlled laboratory conditions and in the dark, but shows the hardiness of SARS-CoV-2 when the conditions are just right.
"Our results show that SARS-CoV-2 can remain infectious on surfaces for long periods of time, adding to the need for best practices like regular hand washing and cleaning of surfaces," said Debbie Eagles, assistant director of the Australian Center for Disease Preparation ( ACDP).
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The team isolated the virus and created a solution called "artificial slime" that contains virus particles in a concentration similar to that found in infected patients. They placed droplets of the mixture on a variety of surfaces, including plastic and paper, stainless steel, cotton, and vinyl banknotes. They have also put glass to the test as used in ATMs, cash registers, and cell phones.
The team's goal was to find out if the virus remained infectious on surfaces after exposure to temperatures of 20, 30, and 40 degrees Celsius (68, 86, and 104 degrees Fahrenheit). They tried the materials at five different times between one hour and 28 days.
Their results showed that the virus can remain viable for at least 28 days at 28 degrees Celsius – similar to the numbers given for the original SARS virus, but longer than previously published data on SARS-CoV-2. An important finding, the researchers write, is the resistance to glass and the ability of SARS-CoV-2 to be picked up by something like a smartphone screen.
However, the team notes that the study was conducted under controlled conditions, which may improve the survival time of the virus. Increasing the temperature decreased the survivability of the virus. At 40 degrees Celsius, SARS-CoV-2 was no longer viable within 48 hours. In the opposite direction, the virus may have an even better chance of survival at even cooler temperatures.
"The research may also help explain the apparent persistence and spread of SARS-CoV-2 in cool environments with high levels of lipid or protein contamination, such as meat processing plants," said Trevor Drew, director of ACDP, who conducted the studies. There have been several cases of COVID-19 outbreaks in meat packing plants in Australia.
The study is adding to the growing body of evidence that SARS-CoV-2 is resilient to the elements, but does not address the debate about transmission via infected surfaces.
"While the exact role of surface transfer, the level of surface contact, and the amount of virus required to infect remain to be determined," Eagles noted. "Determining how long this virus will remain viable on surfaces is critical to developing risk reduction strategies in high-contact areas."
The argument of "fomite transmission" – infection via contaminated surfaces – has surfaced several times in the course of the pandemic, which dates back to March. Several studies have shown that the coronavirus can persist on a variety of surfaces, but it remains unclear how relevant this is outside of the laboratory. In July, a comment published in the prestigious medical journal The Lancet suggested that the risk of transmission via fomites was "exaggerated" as most studies are conducted in laboratories that do not accurately replicate real-world scenarios.
"COVID-19 spreads less often through contact with contaminated surfaces" and affirms that the main mechanisms of infection are via droplets and droplets .
While there may be more stimuli to wipe your smartphone screen with disinfectant, the most important health advice for the majority of the public doesn't change: masking, social distancing, and hand washing.
Update October 11th: Changed heading to reflect quotes, clarified Eagles quote.