Risk of contracting Covid-19 from touching contaminated surfaces less than 1 in 10,000: US CDC

The CDC has previously acknowledged that surfaces are not the primary way that the virus spreads. PHOTO: AFP

NEW YORK (NYTIMES) - When the coronavirus began to spread in the United States last spring, many experts warned of the danger posed by surfaces.

Researchers reported that the virus could survive for days on plastic or stainless steel, and the Centres for Disease Control and Prevention advised that if someone touched one of these contaminated surfaces - and then touched their eyes, nose or mouth - they could become infected.

Americans responded in kind, wiping down groceries, quarantining mail and clearing drugstore shelves of Clorox wipes. Facebook closed two of its offices for a "deep cleaning". New York's Metropolitan Transportation Authority began disinfecting subway cars every night.

But the era of "hygiene theatre" may have come to an unofficial end this week, when the CDC updated its surface cleaning guidelines and noted that the risk of contracting the virus from touching a contaminated surface was less than 1 in 10,000.

"People can be affected with the virus that causes Covid-19 through contact with contaminated surfaces and objects," Dr Rochelle Walensky, the director of the CDC, said at a White House briefing on Monday.

"However, evidence has demonstrated that the risk by this route of infection of transmission is actually low."

The admission is long overdue, scientists say.

"Finally," said Linsey Marr, an expert on airborne viruses at Virginia Tech. "We've known this for a long time and yet people are still focusing so much on surface cleaning."

She added, "There's really no evidence that anyone has ever gotten Covid-19 by touching a contaminated surface."

During the early days of the pandemic, many experts believed that the virus spread primarily through large respiratory droplets. These droplets are too heavy to travel long distances through the air but can fall onto objects and surfaces.

In this context, a focus on scrubbing down every surface seemed to make sense.

"Surface cleaning is more familiar," Marr said. "We know how to do it. You can see people doing it, you see the clean surface. And so I think it makes people feel safer."

But over the last year, it has become increasingly clear that the virus spreads primarily through the air - in both large and small droplets, which can remain aloft longer - and that scouring door handles and subway seats does little to keep people safe.

"The scientific basis for all this concern about surfaces is very slim - slim to none," said Emanuel Goldman, a microbiologist at Rutgers University, who wrote last summer that the risk of surface transmission had been overblown.

"This is a virus you get by breathing. It's not a virus you get by touching."

The CDC has previously acknowledged that surfaces are not the primary way that the virus spreads. But the agency's statements this week went further.

"The most important part of this update is that they're clearly communicating to the public the correct, low risk from surfaces, which is not a message that has been clearly communicated for the past year," said Joseph Allen, a building safety expert at the Harvard T.H. Chan School of Public Health.

Catching the virus from surfaces remains theoretically possible, he noted. But it requires many things to go wrong: a lot of fresh, infectious viral particles to be deposited on a surface, and then for a relatively large quantity of them to be quickly transferred to someone's hand and then to their face. "Presence on a surface does not equal risk," Allen said.

Still, the guidelines do suggest that if someone who has Covid-19 has been in a particular space within the last day, the area should be both cleaned and disinfected.

"Disinfection is only recommended in indoor settings - schools and homes - where there has been a suspected or confirmed case of Covid-19 within the last 24 hours," Walensky said during the White House briefing.

"Also, in most cases, fogging, fumigation and wide-area or electrostatic spraying is not recommended as a primary method of disinfection and has several safety risks to consider."

Allen said that the school and business officials he has spoken with this week expressed relief over the updated guidelines, which will allow them to pull back on some of their intensive cleaning regimens. "This frees up a lot of organisations to spend that money better," he said.

Schools, businesses and other institutions that want to keep people safe should shift their attention from surfaces to air quality, he said, and invest in improved ventilation and filtration.

"This should be the end of deep cleaning," Allen said, noting that the misplaced focus on surfaces has had real costs.

"It has led to closed playgrounds, it has led to taking nets off basketball courts, it has led to quarantining books in the library. It has led to entire missed school days for deep cleaning. It has led to not being able to share a pencil. So that's all that hygiene theatre, and it's a direct result of not properly classifying surface transmission as low risk."

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