How to disinfect public surfaces during a pandemic (and whether you even need to)

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In these dark and confusing times, hygiene is undergoing something of a renaissance.

Since COVID-19 made landfall in the U.S. this January, disinfecting sprays and wipes have flown off shelves, triggering shortages nationwide as concerned citizens scramble to sanitize the countless surfaces they touch. From subway poles to shopping carts and doorknobs, few objects have been spared.

With hygiene heroes like hand-washing already on our side, this frenzied cleaning craze might seem like overkill. And, to be clear, disinfecting common spaces is not a replacement for thoroughly sudsing up your grubby mitts with soap. But in the spirit of limiting exposure to this new coronavirus, called SARS-CoV-2, we could all be a little more conscientious about sanitizing the things in our environments we touch most often—especially with our bare hands.

These behaviors are especially relevant now that researchers have some evidence that, with the right temperature and humidity, SARS-CoV-2 can remain infectious for quite a long time after it’s sneezed or coughed out of an infected individual. In recently reported laboratory experiments—which have yet to be published in a peer-reviewed journal—scientists puffed the pathogen into air or applied it to a series of surfaces. Under these strictly controlled conditions, the virus remained detectable up to three hours in the air, up to a day on cardboard, and up to three days on plastic and stainless steel.

The real world is far more chaotic than the inside of a lab, and viral viability will undoubtedly vary from place to place. But these estimates still leave plenty of time for the virus to accumulate on surfaces made of these materials, from subway poles to gym equipment, says Elodie Ghedin, a virologist and epidemiologist at New York University’s School of Global Public Health. From there, SARS-CoV-2 can easily contaminate your hands and hitch a ride into your body when you touch your eyes, nose, or mouth.

Luckily, this particular virus is a vulnerable one. Earlier this month, the Environmental Protection Agency published a hefty list of disinfectants with ingredients known to destroy coronaviruses like SARS-CoV-2. Many of them contain ethyl alcohol, isopropyl alcohol, or a bit of bleach as their active agent. All three of these chemicals are commonly used in microbiology labs, and work by wreaking havoc on proteins—the basic units that keep cells and viruses functioning. Alcohols can also disrupt the fatty outer coatings that shroud many viruses, including SARS-CoV-2, preventing them from latching onto and invading new cells.

Not all formulations will work, though. Be wary of products that rely solely on chlorhexidine, a common antimicrobial that works on many pathogens but appears to leave coronaviruses intact. Another dead end? Things that contain only antibiotics, which act against bacteria, not viruses.

Pick your chemicals carefully

Sprayed liberally onto a surface, many disinfectants need only seconds to start their not-so-dirty work, says Efraín Rivera Serrano, a virologist at the University of North Carolina at Chapel Hill. But people should wait several minutes to let the liquids engulf and destroy the microbes before wiping them away. “It’s a chemical reaction,” Rivera Serrano says. “You have to allow time for that.”

Disinfectant wipes can work too, he adds, though they need to be well-soaked to actually serve up enough of the necessary chemical cocktail to dispatch the pathogens in question. Because they pick up entire swaths of microbes, wipes also can’t be reused, making them convenient but wasteful, says Carol Reiss, a virologist at NYU.

If a surface is visibly filthy, though, simply coating it with disinfecting chemicals won’t do much good—all that gunk can cloak and protect the pathogens you’re trying to destroy, says Robyn Gershon, an occupational and environmental health and safety researcher at NYU. Soap and clean water will need to mount the first attack—a solid sudsing will physically strip grit, grime, and germs away. Soap can also damage the same viral envelopes that are sensitive to alcohol. After the schmutz is gone, a thorough spritzing with disinfectant can destroy any infectious stragglers.

Not all surfaces are worth your time

Of course, none of us have time to disinfect every surface we come into contact with—nor is that strategy practical. Both Rivera Serrano and Gershon recommend focusing on the surfaces your bare hands contact most frequently. At home, that might include faucets, light switches, and handles; in the workplace (if you’re still going), things like keyboards, phones, cash registers, and desk surfaces might be in need of a good swab. Less worth your time? Things that contact your heinie but not your hands, like a bus seat.

One oft-forgotten culprit is the omnipresent cell phone, a veritable cesspool of microbes that makes frequent contact with fingers and faces alike. “My cell phone is the object I touch the most,” Ghedin says. “I suspect it’s teeming with stuff. If you clean your hands but not your cell phone, you’re recontaminating your hands every time.”

Most challenging of all, however, are surfaces in public spaces visited by hordes of people on a daily basis: transportation hubs, grocery stores, gyms, and more. Out there, it’s virtually impossible to clean a surface frequently enough to keep it perpetually clean, says Akiko Iwasaki, a virologist at Yale University.

Experts are now stressing the importance of social distancing—literally, staying away from other people (and crowded places) as much as possible to stem the spread of disease. When outings are necessary, you can avoid some contamination by putting physical barriers, like gloves or paper towels, between yourself and commonly touched objects, Gershon says. If your bare hand must make contact, then yes, feel free to go ape with the disinfectant—especially if it puts your mind at ease. But, Gershon stresses, don’t make that your only plan of attack.

Under most circumstances, we can’t control what’s on public surfaces, Gershon says. Instead, prioritize what you do have an immense influence over: the cleanliness of your own body.

Above all, personal hygiene matters most

Contagious as this new coronavirus is, it can’t do its job until it hits your airway and finds some living cells to attack. Touching a contaminated surface does not guarantee infection: SARS-CoV-2 can still be halted in its tracks by a bout of hand-washing or, as a second choice, a slathering of some alcohol-based sanitizer.

In a way, your hands are just another surface to clean and disinfect, and many of the same chemical rules of the road apply: Lathering up and giving your hands a good ol’ 20-second scrub both removes and damages pathogens; when soap and water aren’t available, hand sanitizers with at least 60 percent alcohol content can blitz many of those same bugs out of existence, as long as you let the gel fully air-dry on your skin. But don’t spray disinfectants on your skin, especially those containing bleach, which is no friend to living cells. Following the instructions on a label is always a good idea.

“You have a better chance of protecting yourself by protecting you than protecting a seat or a pole,” Gershon says. Keeping your distance, and your hands clean—“really, that’s about all you can do.”