“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 C.D.C. has previously acknowledged that surfaces are not the primary way that the virus spreads. But the agency’s statements this week went farther.
“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,” Dr. 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 C.D.C.’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 Covid-19 has been in a particular space within the last day, the area should be both cleaned and disinfected.