Coronavirus stays infective in air for hours, on surfaces for days

The novel coronavirus that has killed about 8,000 and infected 200,000 people worldwide stays infectious in aerosols for several hours and on surfaces for days, says a breakthrough study that explains how the pathogen spreads quickly through infected droplets and from contact with contaminated surfaces.

Sars-CoV-2, the virus that causes the Covid-19 disease, is detectable for up to three hours in aerosols, up to four hours on a copper surface, up to 24 hours on cardboard, and up to two-three days on plastic and stainless steel, found the study published in the peer-reviewed New England Journal of Medicine (NEJM).

It compared the stability of Sars-Cov-2 in the environment with that of Sars-Cov, which caused the Severe Acute Respiratory Syndrome (Sars) outbreak that sickened close to 8,000 people in 2002-2003.

Scientists say both viruses are closely related. No Sars case has been detected since 2004.

The study found that the stability, or the duration a virus is live in the environment, of Sars-CoV-2 was similar to that of Sars-CoV in experimental circumstances tested. But unlike Sars, which was contained through intensive contact tracing and case isolation measures, the ongoing community transmission of Covid-19 in several countries has turned it into a pandemic.

Community transmission is when a person tests positive for the disease but doctors are not able to trace the source of the infection.

"This indicates that differences in the epidemiologic characteristics of these viruses probably arise from other factors, including high viral loads in the upper respiratory tract and the potential for persons infected with Sars-CoV-2 to shed and transmit the virus while asymptomatic," said the study published on Wednesday.

The study warned of the dangers of Covid-19 spreading from people who do not have symptoms or those with mild symptoms, an occurrence confirmed in another study from China that found for every confirmed case in China, there are another five to 10 people in the community with mild, undetected symptoms. These undiagnosed cases were the source of 79% of reported infections in China before a lockdown was imposed on January 23, said the study published in the journal, Science, on Tuesday.

Another big difference between the two viruses is that Covid-19 is spreading in community settings, unlike Sars, which caused outbreaks in clusters in hospitals. "If viral shedding is high, there will be higher concentration of aerosols in the air and on surfaces, which makes the risk of transmission higher in hospital settings compared to other groups," said Dr G Anil K Prasad, professor and former head of respiratory virology at Vallabhai Patel Chest Institute, University of Delhi.

(Inputs and image from hindustantimes.com)