Coronavirus infectious on surfaces after 28 days- study

Coronavirus can remain infectious on surfaces for 28 days, a study by Australia’s national agency has revealed.

The study which was titled: “The effect of temperature on the persistence of SARS-CoV-2 on common surfaces”, sought to examine the roles played by objects, known as fomite, in transmitting the virus. It was published on the Virology Journal on October 7, 2020.

The test involved subjecting the virus to varied temperature conditions to examine its ability to stay alive and infectious.  The study, which was conducted by Peter Doherty Institute was “carried out in the dark, to negate any effects of UV light.” Also, the study revealed that “inoculated surfaces were incubated at 20 °C, 30 °C and 40 °C and sampled at various time points.”

The research focused on using the banknotes, common surfaces like the stainless steel, cotton cloths, glass and among other surfaces to determine their levels of infectiousness when exposed to the virus.

The study notes: “Australian polymer banknotes, de-monetised paper banknotes and common surfaces including brushed stainless steel, glass, vinyl and cotton cloth were used as substrates in this study. Both polymer and paper banknotes were included in the study to gather information on the possible roles of note based currency in general for the potential for fomite transmission.

Stainless steel is used in kitchen areas and public facilities and is the substrate used in some disinfectant testing standards.”

The experiment also covered high-risk areas such as hospitals and transport systems which people frequent.

“Glass was chosen due to its prevalence in public areas, including hospital waiting rooms, public transport windows and shopping centres, and high contact surfaces such as mobile phone screens, ATMs and self-serve check-out machines.

Vinyl is a common substrate used in social settings, tables, flooring, grab handles on public transport, as well as mobile phone screen protector material,” the study notes.

Survival varies

According to the study results, at 20 °C, the coronavirus (SARS-CoV-2) survived in non-porous surfaces for 28 days.

“At 20 °C, infectious SARS-CoV-2 virus was still detectable after 28 days post-inoculation, for all non-porous surfaces tested (glass, polymer note, stainless steel, vinyl and paper notes). The recovery of SARS-CoV-2 on porous material (cotton cloth) was reduced compared with most non-porous surfaces, with no infectious virus recovered past day 14 post-inoculation,” the study reveals.

The study findings indicated that the survival of the Covid-19 causing virus reduced with the intensity of temperature. This was manifested in the reduced number of days the virus remained in infectious. It was determined that at 30 °C, the virus had slightly shorter lifespan on the surfaces.

“At 30 °C, infectious virus was recoverable for 7 days from stainless steel, polymer notes and glass, and 3 days for vinyl and cotton cloth. For paper notes, infectious virus was detected for 21 days, although there was less than 1 log of virus recovered for both 14 day and 21 day time points, said the study.

The study showed that at 40 °C, “infectious SARS-CoV-2 was not recovered past 24 hours for cotton cloth and 48 hours for all remaining surfaces tested.”

The study concludes that the virus can stay alive for four weeks but such days of survivability are reduced when temperature increases above 20 °C but humidity is maintained.

World Health Organisation (WHO) states on its website that the virus has so far infected 37 million people and killed 1.07 million others since its outbreak in Wuhan City, China, last year.

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