Transmission of SARS-CoV-2 via surfaces
The role of transmission of SARS-CoV-2, the virus that causes COVID-19, by touching contaminated surfaces is not yet fully understood.
Studies have shown that high contact surfaces such as touchscreens on mobile phones, bank ATMs, airport check-in kiosks and supermarket self-serve kiosks can all act as potentially contaminated surfaces for the transmission of viruses.
Understanding SARS-CoV-2 on surfaces
To improve our understanding of how this new virus behaves, our researchers studied the survival of infectious SARS-CoV-2, suspended in an artificial mucous, on six common surfaces.
The experiment was carried out at three different temperatures, 20°C, 30°C and 40°C with the relative humidity kept at approximately 50%.
The surfaces used in the study were stainless steel, glass, vinyl, paper and polymer banknotes and cotton cloth.
We considered these surfaces to be examples of potentially high-contact areas, such as glass on touchscreens on mobile devices and supermarket self-service kiosks. Stainless steel is often seen used for doorknobs and vinyl is frequently used on public transport seats and grab rails.
Cotton, often used for bedding and clothing, was chosen as a porous surface in comparison to the non-porous surfaces examined.
A droplet of fluid containing the virus at concentrations similar to levels observed in infected patients was placed on multiple small test surfaces and left for up to 28 days. At various time periods, the virus was recovered and placed in tissue culture cells to observe if any infectious virus remained.
At 20°C we found that the virus was extremely robust. We were able to recover infectious material at 28 days from all the smooth (non-porous) surfaces. These are stainless steel, glass, vinyl, and paper and polymer banknotes. The recovery of SARS-CoV-2 from the porous material (cotton cloth) at 20°C was much shorter with no viable virus surviving past 14 days.
At 30°C infectious virus was recoverable for only seven days from stainless steel, money (polymer banknotes) and glass. It was recoverable for only three days from vinyl and cotton cloth.
At 40°C virus was inactivated much more quickly. Infectious SARS-CoV-2 was detectable for less than 16 hours for cotton cloth, up to 24 hours for glass, stainless steel, paper and polymer notes and 48 hours for vinyl.
From our data, we can also conclude that the virus will survive even longer at colder temperatures (less than 20°C). This may help to explain the apparent persistence and spread of SARS-CoV-2 in cool environments, such as meat processing facilities.
The risk of surface transmission
While the main method of spread of SARS-CoV-2 is via aerosols and respiratory droplets, our results indicate that high-contact surfaces may pose a risk.
However, viruses do not penetrate skin and to transfer the virus from a surface requires that a person introduce it into their mouth, nose or eyes.
Therefore, continue to disinfect surfaces, particularly in the workplace, wash your hands regularly and avoid touching your eyes, nose and mouth.