Seven months after the novel coronavirus was declared as a pandemic, new scientific evidence finds that SARS-CoV-2 can last on currency, glasses, and stainless steel for 28 days at 20º C under laboratory conditions. Earlier research found that the virus could last on surfaces for several days but its transmission through surfaces is less understood.
When compared to other viruses, SARS-CoV-2 is more resilient on surfaces. Influenza virus is only viable for 17-22 days on these surfaces, the researchers noted.
The study conducted by scientists at Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) also found that the virus barely survived for 24 hours at higher temperatures of 40ºC. This study was performed in the dark so as to negate the effects of UV light.
Published in the Virology journal, the study provides an impetus to the World Health Organisation's (WHO) constant reminders to focus on non-pharmacological interventions of sanitising surfaces and inculcating the practice of continuous hand-washing. So far, the virus is known to transmit through air in the form of aerosols as well as airborne droplets.
The Centers of Diseases Control and Prevention, US' apex research body, has also published on its website that the virus is more likely to spread through closed and poorly ventilated areas and human-human transmission. Fomite transmission, which is transmission through surfaces is considered as a less likely mode of transmission.
"Even though the exact nature 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," said Dr. Debbie Eagles, one of the researchers in a press release.
What Does The Study Find
To assess the survival rates of SARS-CoV-2 at various temperatures, the scientists isolated the SARS-CoV-2 strain, chemically dried it to match the concentrations found in patients and inoculated them into porous (cotton cloth) and non-porous (Australian polymer bank notes, de-monetised paper bank notes, stainless steel, glass, vinyl) and isolated at 20º, 30º and 40º.
All the isolates were prepared in the dark as the researchers wanted to negate the effect of UV light as several theories state that the virus is inactivated in sunlight. Post- inoculation, the samples were tested after 1 hour, 1 day, 2 days, 3 days, 4 days, 7 days, 14 days, and 28 days.
In the 20º isolates, the virus was inactivated on cotton cloth by the 14th day, but was still active on glass, stainless steel, vinyl surfaces, and both paper and polymer bank notes till the 28th day. It stayed active on paper notes for longer than the polymer notes.
Notably, in the isolates kept at 40 degrees, the virus was inactivated from all the surfaces within 24-48 hours thus supporting the theory that the virus is inactivated at higher temperatures.
How Are These Findings Useful
BOOM earlier reported that at the beginning of the pandemic, preliminary research showed that the virus survived on several surfaces such as stainless steel, copper, and plastic for up to 72 hours.
China, United States, and South Korea announced decontaminating currency notes at the onset of the pandemic. According to the Australian researchers, the virus stays more active on paper notes over polymer notes, thus strengthening the evidence that the virus can transmit through currency.
Furthermore, the researchers chose glass as its the most commonly found surface. The researchers emphasised the importance of cleaning glass surfaces and using touchscreen phones only after sanitising one's hands in the discussion of the study. They also recommend that all glass surfaces at banks, airports and even mobile screens should be regularly disinfected.
Along with the findings on stainless steel, cotton, and vinyl, the researchers believe that their findings will allow the formulation of better risk mitigation techniques that will help in COVID-19 management.
