Ten months into the coronavirus disease (COVID-19) pandemic, scientists learn more about the virus on a daily basis.
Previously, studies have pointed out that the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can persist on surfaces for days. Now, a new study provides an alarming finding that the virus can persist on surfaces for up to 28 days.
Published in the Virology Journal, the study shows that the virus can stay infectious for more extended periods on surfaces such as phone screens, stainless steel, and banknotes than previously thought.
A team of researchers at the Australian Centre for Disease Preparedness aimed to determine the role of fomite transmission in the spread of the SARS-CoV-2 virus across the globe, which has now infected more than 37.68 million people worldwide, according to the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University (JHU).
In the study, the team measured the survival rates of infections SARS-CoV-2, suspended in a standard ASTM E2197 matrix, on many common types of surfaces. The team carried out the experiments in the dark to negate the effects of ultraviolet light. Further, the researchers incubated the inoculated surfaces at 20 °C, 30 °C and 40 °C.
The team obtained the virus isolate used in the study by the Peter Doherty Institute on behalf of the South Australian Health. All the experiments with the infectious virus isolate were performed in the high containment laboratory (Biosafety level 4) at the Australian Centre for Disease Preparedness.
The team used commonly touched surfaces and items to see how long the infectious virus particles could survive. They used Australian polymer banknotes, de-monetized paper banknotes, and common surfaces, including glass, cotton cloth, and brushed stainless steel.
Paper and polymer banknotes were also included to determine the role of note-based currency for the potential for fomite transmission. Also, stainless steel is commonly used in kitchen areas and other public facilities. At the same time, glass was chosen due to its prevalence in public areas, and it is used as a screen for mobile phones, ATMs, and other public items, such as tables, public transport windows, and hospital waiting rooms, among others.
The team also used vinyl since it is also a widely used material used in grab handles on public transport, tables, and flooring. Meanwhile, cotton was tested since it is used in clothing, household fabrics, and beddings.
What the study found
The researchers determined the survival rates of SARS-CoV-2 at different temperatures. They obtained half-lives of between 1.7 and 2.7 days at 20 °C, decreasing to a few hours when the temperature was increased to 40 °C.
The virus also persisted on most surfaces for about six to seven days before starting to lose its potency. After two weeks, the team still found many live and infectious virus particles, which could still infect people.
The team also found that a viable virus was isolated for up to 28 days at 20°C from common surfaces like stainless steel, glass, and both paper and polymer banknotes. However, the infectious virus survived less than 24 hours at 40 °C on some surfaces.
“These findings demonstrate SARS-CoV-2 can remain infectious for significantly longer periods than generally considered possible. These results could be used to inform improved risk mitigation procedures to prevent the fomite spread of COVID-19,” the team concluded.
The team added that while the primary spread of SARS-CoV-2 appears to be through aerosols and respiratory droplets, fomites may also play a pivotal role in virus transmission. Fomite transmission has been shown as an important factor in the spread of other coronaviruses, such as the porcine epidemic diarrhea virus, the Middle East Respiratory Syndrome (MERS) coronavirus, human coronavirus 229E and OC43, and the current SARS-CoV-2.
“Increasing the temperature while maintaining humidity drastically reduced the survivability of the virus to as little as 24 h at 40 °C,” the researchers explained.
“The persistence of SARS-CoV-2 demonstrated in this study is pertinent to the public health and transport sectors. This data should be considered in strategies designed to mitigate the risk of fomite transmission during the current pandemic response,” they added.
Health experts and agencies reiterate the importance of regular handwashing, wearing masks, and social distancing to reduce the spread of the coronavirus. It is essential to practice proper hand hygiene, especially after touching common items and surfaces to reduce the risk of being infected with COVID-19, which has now killed more than a million people globally.