The end of overzealous cleaning?
In revised guidance, CDC says risk from surfaces is quite low
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 Centers 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.
But the era of “hygiene theater” 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 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 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.
In most cases, cleaning with simple soap and water — in addition to hand-washing and mask-wearing — is enough to keep the odds of surface transmission low, the CDC’s updated cleaning guidelines say. In most everyday scenarios and environments, people do not need to use chemical disinfectants, the agency notes.
“What this does very usefully, I think, is tell us what we don’t need to do,” said Donald Milton, an aerosol scientist at the University of Maryland. “Doing a lot of spraying and misting of chemicals isn’t helpful.”
Still, the guidelines do suggest that if someone who has COVID19 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 widearea or electrostatic spraying is not recommended as a primary method of disinfection and has several safety risks to consider.”