Coronavirus can survive up to 28 days on surfaces like glass, banknotes and stainless steel, finds study
While the precise role of surface transmission and the amount of virus required for infection is yet to be determined, establishing how long this virus remains viable on surfaces is critical
The virus that causes Covid-19 can survive on common surfaces such as banknotes, glass, and stainless steel, for up to 28 days, about 10 days longer than flu, and lower temperatures give it a longer life, according to researchers. Based on the findings, they say that while the primary spread of the SARS-CoV-2 appears to be via aerosols and respiratory droplets, fomites (objects or materials that may be contaminated with infectious agents) may also be an important contributor to transmission of the virus. The results should be considered in strategies designed to mitigate the risk of fomite transmission during the current pandemic response, recommends the team from the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia's national science agency.
The study investigated how long SARS-CoV-2 can remain infectious on common surfaces and the results were obtained under laboratory conditions. The analysis reveals that the novel coronavirus survived longer at lower temperatures, tended to survive longer on non-porous or smooth surfaces such as glass, stainless steel and vinyl, compared to porous complex surfaces such as cotton and survived longer on paper banknotes than plastic banknotes. In comparison, similar experiments have found that the flu virus (Influenza A) can survive on surfaces for 17 days. The results demonstrate that SARS-CoV-2 can remain infectious for significantly longer periods than generally considered possible, the authors suggest.
“Our results show that SARS-CoV-2 can remain infectious on surfaces for long periods of time, reinforcing the need for good practices such as regular handwashing and cleaning surfaces. At 20 degrees Celsius, which is about room temperature, we found that the virus was extremely robust, surviving for 28 days on smooth surfaces such as glass found on mobile phone screens and plastic banknotes. For context, similar experiments for Influenza A have found that it survived on surfaces for 17 days, which highlights just how resilient SARS-CoV-2 is,” explains Dr Debbie Eagles is Deputy Director of the Australian Centre for Disease Preparedness (ACDP) in Geelong, where the research was undertaken. The findings have been published in the Virology Journal.
Professor Trevor Drew, ACDP director, suggests that the report may also help to explain the apparent persistence and spread of SARS-CoV-2 in cool environments, such as meat processing facilities and how that risk might be better addressed.
Infections with respiratory viruses are principally transmitted through three modes: contact, droplet, and airborne. Contact transmission is infection spread through direct contact with an infectious person or with an article or surface that has become contaminated. The latter is sometimes referred to as fomite transmission. Droplet transmission is infection spread through exposure to virus-containing respiratory droplets exhaled by an infectious person. Airborne transmission is infection spread through exposure to those virus-containing respiratory droplets composed of smaller droplets and particles that can remain suspended in the air over long distances and time. SARS-CoV-2 is a new virus and scientists are still learning about how it behaves. According to the US Centers for Disease Control and Prevention (CDC), it is much more common for SARS-CoV-2 to spread through close contact with a person who has Covid-19 than through airborne transmission. It also suggests that coronavirus spreads less commonly through contact with contaminated surfaces.
While the precise role of surface transmission, the degree of surface contact, and the amount of virus required for infection is yet to be determined, establishing how long this virus remains viable on surfaces is critical for developing risk mitigation strategies in high contact areas, the team explains. “The rate at which Covid-19 has spread throughout the globe has been alarming. While the role of fomite transmission is not yet fully understood, precise data on the environmental stability of SARS-CoV-2 is required to determine the risks of fomite transmission from contaminated surfaces,” they say.
The analysis involved drying virus in an artificial mucus on different surfaces, at concentrations similar to those reported in samples from infected patients, and then re-isolating the virus over a month. Further experiments were carried out at 30 and 40 degrees Celsius, with survival times decreasing as the temperature increased. Increasing the temperature while maintaining humidity drastically reduced the survivability of the virus to as little as 24 hours at 40°C. The study was also carried out in the dark, to remove the effect of UV light as research has demonstrated direct sunlight can rapidly inactivate the virus.
According to the authors, the persistence of SARS-CoV-2 demonstrated in this study is pertinent to the public health and transport sectors. They emphasize that the persistence of the coronavirus on both paper and polymer currency is of particular significance, considering the frequency of circulation and the potential for transfer of viable virus both between individuals and geographic locations. The persistence on glass is also an important finding, given that touchscreen devices such as mobile phones, bank ATMs, supermarket self-serve checkouts and airport check-in kiosks are high touch surfaces that may not be regularly cleaned and therefore, pose a transmission risk of Covid-19, they add. “Establishing how long the virus really remains viable on surfaces enables us to more accurately predict and mitigate its spread and do a better job of protecting people,” concludes CSIRO Chief Executive Dr Larry Marshall.