Although studies continue to show that the novel coronavirus can be detected on contaminated objects after days or weeks, a consensus has emerged among scientists that the virus is rarely transmitted through contact with tainted surfaces and that it’s safe to stop taking such extreme measures as quarantining your mail and wiping down your groceries.

“To the best of my knowledge, in real life, scientists like me — an epidemiologist and a physician — and virologists basically don’t worry too much about these things,” said David Morens, a senior adviser to the director of the National Institute of Allergy and Infectious Diseases, Anthony S. Fauci.

That’s in line with advice from the Centers for Disease Control and Prevention, which has updated its “How Covid-19 Spreads” Web page to say that “spread from touching surfaces is not thought to be a common way” the virus is transmitted.

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Although ongoing research can sound alarming — such as an Australian study published Oct. 7, which found that SARS-CoV-2 could be detected on surfaces such as glass and stainless steel after 28 days — Morens said the public should not be concerned.

Such studies “basically tend to show that under experimental conditions, which are not real-world conditions, you can get virus to persist and you can detect that persistence,” he said. But, he added, that doesn’t mean the virus could infect anyone. “The amount of virus that can persist might not be the amount of virus that can affect you in a real-world environment.” In the real world, airflow, sunlight and heat all act quickly to weaken the coronavirus.

Stefan Baral, an associate professor in the department of epidemiology at the Johns Hopkins Bloomberg School of Public Health, said there’s a big difference between a single viral particle being able to survive on a particular surface, and the ability of a virus to enter a mucus membrane, cross that mucus membrane and successfully replicate and infect someone. “A single viral particle is exquisitely unlikely to cause serious effect,” he said.

Those with compromised immune systems are especially vulnerable as covid-19 continues to spread. Northwestern University's Melinda Ring explains why. (The Washington Post)

But public confusion about the coronavirus and surfaces is understandable, said Angela Rasmussen, a virologist at the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health. “Scientists really haven’t really done a very good job of explaining how you get evidence for different types of transmission or different transmission routes.”

Rasmussen said epidemiologists can have a difficult time finding real-word evidence of a virus’s transmission via contaminated objects or surfaces, which are called fomites. In the case of the coronavirus, this is partly because transmission often occurs in the context of large, superspreader events, leaving researchers struggling to determine who talked to whom, and who touched what surface. “It’s not at all uncommon to not have strong epidemiological evidence for fomite transmission,” she said, “but that doesn’t mean that fomite transmission doesn’t happen.”

In fact, Rasmussen added, because we know that other respiratory viruses that are transmitted by inhalation, such as the flu and rhinovirus, are also transmitted by fomites, it stands to reason that coronavirus is probably transmitted by fomites, too. “It just may be that that’s not necessarily the dominant mode of transmission,” she said. And although it may be important for researchers to determine how long the virus remains infectious in various environments, when it comes to daily life, “I don’t think that it’s necessarily wise to be wiping groceries down.”

Morens agrees. “There’s just a lot of unnecessary worry about these things,” he said. “It’s like standing in the middle of a busy freeway with traffic all around you and asking, ‘What’s the chance I’m going to get hit by a meteor?’ Now there’s a chance, but it’s pretty low, and don’t you have other better things to worry about?”

Although no environment can be determined to be totally safe, Morens says we need to think about actions as low-, medium- or high-risk. The times to worry about contaminated surfaces would be when you are in a crowded public place where many people are touching the same surfaces. As an illustration of an area that poses high risk, he cited a public restroom next to a crowded airport lounge, where possibly contaminated people might touch the door handle, light switch, towel dispenser and faucet. That’s a situation where you should be super-alert; if you wash your hands and then touch the faucet or door handle again, for example, you’ve just possibly contaminated yourself.

Protection is not gained by washing down everything in the environment, Morens said. “It’s the behaviors you do to make sure that nothing in the environment, including your own hands, gets into your mouth, nose or eyes.”

Those behaviors include never touching yourself above the neck, wearing a mask (which also helps remind you not to touch your face), social distancing and making sure your hands are as clean as possible. In that case, you could even go into a restaurant and touch objects there — the chair, the menu — without wiping them down first, and “if the very last thing you touch is soap and water or hand sanitizer, . . . you’re okay,” Morens said.

Baral, who has been pushing for the reopening of playgrounds, said that one of the factors he considers when deciding whether a situation is high-risk is the environment the virus might find itself in. “These viruses do not survive well outdoors,” he said. Coronaviruses like to be surrounded by fluid to protect them, and fluid evaporates pretty quickly outside — leaving the virus vulnerable to the elements. He noted that outdoor playgrounds, which have not historically been known as high-risk settings for other viruses, have not been identified as areas of common exposure for the coronavirus, months into the pandemic, which he finds “striking.”

However, Baral doesn’t feel the same way about indoor environments. There may be environments in people’s homes where the virus does well and lives on surfaces, he said. For that reason, people should immediately wash their hands as soon as they enter their home from the outside and frequently disinfect common surfaces, such as doorknobs and faucets.

But could all the sanitizer and disinfectant being used to clean hands and high-touch surfaces be paving the way for antibiotic-resistant “superbugs?” Not if you’re using soap and water or the products recommended by the World Health Organization and the CDC, which are alcohol- or bleach-based — and not those labeled antibacterial, Rasmussen says. Antibacterial products are the ones that can encourage the development of drug-resistant germs — and they don’t kill viruses, anyway.

Soap and water, alcohol and bleach, on the other hand, work in a broad-spectrum way, Rasmussen said, and kill many bacteria and viruses. She believes there’s really no need for antibacterial cleaners in the household. “It’s unfortunate that for a while they were very popular on the consumer market,” she said. “But you can use soap and these other types of disinfectants that are more general and that won’t select for resistance.”

Finally, she said, it’s important to remember that “viruses have to have a host, and they can’t replicate without one. So . . . the main place that’s going to be the source of virus in anybody’s household is going to be the people in it and not the surfaces or the physical environment.”

“Even if there’s virus kicking around on certain things,” she said, “that risk can really be mitigated practically by washing your hands.”