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Coronavirus | How long does SARS-CoV-2 stay potent?

French firefighters in Marseille on April 3, 2020 work at the PCR machine on a mobile unit, which can detect the presence of SARS-CoV-2 in the environment.   | Photo Credit: AFP

The story so far: With a nascent virus, SARS-CoV-2, causing a global pandemic, the scramble has been, so far, and will be for a time to come, to understand the virus. While it belongs to the coronavirus family — variants of which cause the common cold — scientists and health-care workers are trying to fathom the nature of the virus, its behaviour and patterns, and gain familiarity with the pathogen, hoping that it will give them a better handle on this pandemic. It is known that coronaviruses, which primarily affect the upper respiratory tract in people, are transmitted through respiratory droplets. The simple act of being close to persons who sneeze or cough, even speak loudly (if they are carrying the infection) and the involuntary act of touching surfaces where the viruses have been deposited can infect someone. The period that the virus remains on the surface and remains capable of spreading infection, can be considered the period for which the virus is viable.

Watch | How long does SARS-CoV-2 stay potent?
 

What guides our understanding of viability?

The Atlanta-headquartered Centers for Disease Control (CDC) has said that current evidence suggests that SARS-CoV-2 may remain viable for hours to days on surfaces made from a variety of materials. Information listed on the CDC website says: “Cleaning of visibly dirty surfaces followed by disinfection is a best practice measure for prevention of COVID-19 and other viral respiratory illnesses in households and community settings.”

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One of the studies that guides our understanding of the viability of SARS-CoV-2 was done by the National Institutes of Health, CDC, UCLA and Princeton University scientists who found that SARS-CoV-2 was detectable in aerosols for up to three hours, up to four hours on copper, up to 24 hours on cardboard and the longest — up to two to three days — on plastic and stainless steel. The study was published in The New England Journal of Medicine on March 17, 2020 (https://bit.ly/3dTewEN), and postulated that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1, but also that the novel coronavirus was more stable.

The researchers wrote: “SARS-CoV-2 remained viable in aerosols throughout the duration of our experiment (3 hours)… Our results indicate that aerosol and fomite (materials capable of transmitting the infection) transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days.”

An analysis by the CDC on the cruise ship Diamond Princess which had 3,700 passengers and which was quarantined after a large number of them developed COVID-19, showed that the SARS-CoV-2 RNA was found on surfaces in the cabins of people who were infected, for up to 17 days after the passengers disembarked, and before disinfection procedures were initiated. However, the analysis mentioned that “data cannot be used to determine whether transmission occurred from contaminated surfaces,” meaning the scientists were not the wiser about whether the virus on the surfaces infected people on the ship.

Coronavirus | How long does SARS-CoV-2 stay potent?
 

Scientists are trying to estimate the decay rate of the virus on various surfaces to determine how long they will be potent or capable of spreading the infection to others who come into contact with the surfaces. There are, of course, no rules about survival on surfaces, since everything depends intensely on the environment as well.

The World Health Organisation (WHO), reacting to a global fear of the infection spreading via newspapers, said: “The likelihood of an infected person contaminating commercial goods is low and the risk of catching the virus that causes COVID-19 from a package that has been moved, and exposed to different conditions and temperatures is also low.” Additionally, the International News Media Association has recorded that there has never been a documented incident whereby the COVID-19 virus has been transmitted from a print newspaper, print magazine, print letter, or print package, citing doctors and scientists.

Coronavirus | How safe are newspapers, WHO clarifies

The good news, scientists say, is that by themselves, viruses are not capable of multiplying; they need a host for that. So disinfecting surfaces, and practising hand hygiene, besides avoiding touching the face, will greatly reduce the chances of people catching infection from surfaces that are not reinfected.

What is the solution?

Disinfection helps in reducing the viral load in the environment, public health experts say. A 1 % hypochlorite solution is an effective disinfectant on various surfaces.

 

Presently, massive disinfection efforts are being carried out in public places as a control measure. This is assuming that people would have spit in the open or sneezed without covering their mouth.

Floors, walls and surfaces frequently touched by hands should be disinfected as per guidelines. This is because handrails of staircases, elevators, door handles, armrests of chairs, table surfaces can be contaminated by droplets.

The CDC has also recorded on its website: It is unknown how long the air inside a room occupied by someone with confirmed COVID-19 remains potentially infectious. Facilities will need to consider factors such as the size of the room and the ventilation system design (including flowrate [air changes per hour] and location of supply and exhaust vents) when deciding how long to close off rooms or areas used by ill persons before beginning disinfection. Taking measures to improve ventilation in an area or room where someone was ill or suspected to be ill with COVID-19 will help shorten the time it takes respiratory droplets to be removed from the air.

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Is there something that people can do themselves?

A good part of avoiding COVID-19 infection indeed rests on each and every individual. Following hand hygiene —washing hands frequently with soaps and sanitisers is key. Maintaining physical distance between one another is also very important.

Measures such as a lockdown attempt to do precisely this: restrict the access of people to public spots, thereby making sure that there is no opportunity for gatherings in large numbers.

It is important to respect the rules of the lockdown, those under quarantine must remain indoors, since asymptomatic people making sorties outside the home might spread the infection to others.

Watch | What is contact tracing?
 

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Printable version | Jan 23, 2021 8:13:11 AM | https://www.thehindu.com/sci-tech/health/how-long-does-sars-cov-2-stay-potent/article31259761.ece

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