It’s Time to Talk About Covid-19 and Surfaces Again

“In my opinion, the chance of transmission through inanimate surfaces is very small, and only in instances where an infected person coughs or sneezes on the surface, and someone else touches that surface soon after the cough or sneeze (within 1–2 h),” he wrote. “I do not disagree with erring on the side of caution, but this can go to extremes not justified by the data.”

That was months ago, and since then the scientific evidence has tipped in Goldman’s favor. And yet, here we are all the same, wiping down pews and hiding away books, among countless other disinfection rituals molded by those early perceptions. “What’s done cannot be undone,” Goldman tells me now. “And it’s going to take a lot of time and effort to turn things around.”

In March, I wrote about what we knew at the time about our understanding of surface spread, which was very little. Nearly a year into the Covid-19 pandemic, it’s time to ask: What do we know now?

The first widely covered study on fomites and Covid-19, released as a preprint in March by researchers at the University of California, Los Angeles, the National Institutes of Health, and Princeton, was a look at how long the novel coronavirus lasted on different kinds of surfaces. At the time, little was known about how the virus was transmitted, so the question was important. Depending on the material, the researchers could still detect the virus after a few hours on cardboard, and after several days on plastic and steel. They were careful to say that their findings only went as far as that. They were reporting how quickly the virus decayed in a laboratory setting, not whether it could still infect a person or was even a likely mode of transmission.

But in the hazy panic of the time, many people had already taken up fastidious habits: quarantining packages at the door, bleaching boxes of cereal brought back from the store, wearing hospital booties outdoors. A single set of research results didn’t start those behaviors, but—along with other early studies finding the virus on surfaces in hospital rooms and on cruise ships—it appeared to provide validation.

Dylan Morris, a mathematical biologist at Princeton who coauthored the paper, recalls watching what he calls “the great fomite freakout” with frustration. The number of days the virus remained detectable on a surface in a lab wasn’t useful for assessing personal risk, he says, because in the real world, that amount would depend on how much there had been to start with and on environmental conditions that they did not test. Plus, the amount of remaining virus doesn’t tell us much about whether it could reasonably get into someone’s airways and cause an infection. “People really picked up on those absolute times to detectability,” he says. “Everyone wants to know the magical time when something becomes safe.” In subsequent research, he says he’s avoided giving hard temporal cutoffs.

Since March, additional studies have painted a picture that is much more subtle and less scary. But like that first study, each can be easily misinterpreted in isolation. One clear takeaway is that, given an adequate initial dose, some amount of the virus can linger for days or even weeks on some surfaces, like glass and plastic, in controlled lab conditions. Emphasis on controlled. For example, earlier this month, an Australian study published in Virology Journal found traces of the virus on plastic banknotes and glass 28 days after exposure. The reaction to that number felt to some like a replay of March: a single study with a bombshell statistic sparked new fears about touchscreens and cash. “To be honest, I thought that we had moved on from this,” says Anne Wyllie, a microbiologist at Yale University.