Back in the early, heady days of the pandemic, surfaces were the thing to worry about. The prevailing scientific wisdom was that the corona virus spread mainly through large droplets, which fell on surfaces that we then touched with our hands, which we then touched with our faces. (At the time, public health officials said masks were unnecessary for the general public.) So we washed our hands until they were raw. We cowered so as not to touch the doorknobs. We went through industrial amounts of hand sanitizer, pressed elevator buttons with keys and pens, and sanitized our groceries, takeout, and mail.
And then we found out that we had everything backwards. The virus did not spread much over surfaces; spread through the air. We understand the dangers of confined spaces, the importance of ventilation, and the difference between a cloth mask and an N95. Meanwhile, we mostly stopped talking about hand washing. The days when you could hear people humming “Happy Birthday” in public toilets are quickly gone. And packet wiping and ostentatious workplace sanitization protocols have become the stuff of protracted hygiene theater.
This whole episode was among the more strange and disorienting changes of the pandemic. Sanitation, that great bastion of public health, saved lives; actually, no, it wasn’t that important for covid. On one level, this face should be seen as a marker of good scientific progress, but it also calls into question the kinds of actions we briefly thought were our best available defenses against viruses. If hand washing isn’t as important as we thought it was in March 2020, how important is it?
Any public health professional will be quick to tell you that, please, yes, you should still wash your hands. Emanuel Goldman, a microbiologist at Rutgers School of Medicine in New Jersey, believes that “good hygiene” can protect against a range of viruses that are spread by close contact and touch, such as gastrointestinal viruses. Also, let’s be honest: it’s disgusting to use the bathroom and then refuse to wash, whether you’re going to give someone COVID or not.
Even so, the pandemic has piled up evidence that transmission of the coronavirus via fomites—that is, inanimate contaminated objects or surfaces—plays a much smaller role, and airborne transmission a much larger one, than we once thought. The same is likely true for other respiratory pathogens, such as the flu and the coronaviruses that cause the common cold, Linsey Marr, an environmental engineer and aerosol expert at Virginia Tech, told me.
This knowledge is not entirely new: a 1987 study by researchers at the University of Wisconsin found that a group of men who played poker with “wet” cards contaminated with rhinovirus were not infected, while a group who played with other sick players were. . Now Goldman intends to push this point even further. At a conference in December, he will present a paper arguing that, with rare exceptions such as the RSV, all respiratory pathogens are transmitted mainly through the air. The reason we’ve thought otherwise for so long, he told me, is because our understanding is based on the wrong assumptions. In general, the studies that referred to fomite-centered transmission theories were virus survival studies, which measure how long a virus can survive on a surface. Many of them either used unrealistically large amounts of virus or measured only the presence of the virus’s genetic material, not whether it remained infectious. The “design” of these experiments, he said, “was not suitable for extrapolation to real-life conditions.”
The result, for Goldman, is that surface transmission of respiratory pathogens is “negligible,” probably less than 0.01 percent of all infections. If true, it would mean that your chance of catching the flu or cold from touching something in your everyday life is virtually non-existent. Goldman acknowledged that there is a “spectrum of opinion” on the issue. Marr, for example, wouldn’t go that far: She’s confident that more than half of the transmission of respiratory pathogens is airborne, though she said she wouldn’t be surprised if the ratio was much, much higher — the only number she’d rule out is 100 since.
For now, it’s important to avoid binary thinking about it, Saskia Popescu, an epidemiologist at George Mason University, told me. Fomites, airborne droplets, smaller aerosol particles—all modes of transmission are possible. And the proportional breakdown won’t be the same in every environment, Seema Lakdava, an expert on influenza transmission at Emory University, told me. Fomite transmission may be negligible in the grocery store, but that doesn’t mean it’s negligible in the living room, where kids are constantly touching things and sneezing on things and putting things in their mouths. A consequence of this idea is that certain infection prevention strategies have been shown to be very effective in one context but not in another: frequent table disinfection in a preschool classroom may make a lot of sense; often disinfect the desk in your own private cubicle, less.
Most of the conspicuous cleaning we did at the start of the pandemic was excessive, Popescu said, but she worries that we may have gone a bit overboard, relegating some helpful behaviors — targeted disinfection, even hand washing in some cases — to the hygiene theater category. Regardless of the setting, all the experts I spoke with agreed that these behaviors remain important for combating non-breathing pathogens. Recently, when several members of Marr’s family came down with norovirus, an extremely unpleasant stomach bug that causes vomiting, diarrhea and stomach cramps, she disinfected numerous touch-sensitive surfaces around the house. Imagine that: one of the country’s foremost experts in aerial transmission is wiping down doorknobs and light switches.
Marr is not convinced that we have corrected too much. Hand sanitizers are still plentiful, businesses still advertise their protocols for cleaning surfaces, and air quality still receives relatively little attention. She recently watched a person use their shirt to open a visitor center door without touching the doorknob… and then walk in without a mask. There’s nothing wrong with taking certain precautions to prevent fomite transmission, she said — all of which shouldn’t be dismissed en masse as hygiene theater — as long as they don’t come at the expense of efforts to block airborne transmission. “If you wash your hands extra … then you should also wear a good mask in closed environments with lots of people,” Marr said. “If you’re trying to clean surfaces, then you should try to clean the air.”
On Friday, as respiratory virus season looms, CDC Director Rochelle Walenski tweeted three tips for staying healthy: “Get an up-to-date COVID-19 vaccine and get your annual flu shot,” “Stay home if you’re sick,” and—don’t forget—”Practice good hand hygiene.” She didn’t mention masks or ventilation.