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May 29, 2020

Does the coronavirus spread via doorknobs and elevator buttons? Here's what the evidence says.

Daily Briefing

    CDC earlier this month updated its "How Covid-19 Spreads" website to say the new coronavirus doesn't easily spread via contaminated surfaces—but just how likely are you to catch the virus from a contaminated surface? It's not likely, but also not impossible.

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    CDC updates website

    Earlier this month, CDC updated its site and issued a news release saying that indirect contact from a surface contaminated with the new coronavirus—known as fomite transmission—is a potential way to contract the new coronavirus, but not the most prominent way the virus infects other people. 

    "Based on data from lab studies on Covid-19 and what we know about similar respiratory diseases, it may be possible that a person can get Covid-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes," CDC said, "but this isn't thought to be the main way the virus spreads."

    The change prompted confusion from the public, which Angela Rasmussen, a virologist at the Columbia University Mailman School of Public Health, said was concerning.

    "A persistent problem in this pandemic has been lack of clear messaging from governmental leadership, and this is another unfortunate example of that trend," Rasmussen said. "It could even have a detrimental effect on hand hygiene and encourage complacency about physical distancing or other measures."

    Kristen Nordlund, a spokesperson for CDC, said the agency updated the site based on an internal review and "usability testing." However, she said, "Our transmission language has not changed," adding, "Covid-19 spreads mainly through close contact from person to person."

    The most likely way the new coronavirus spreads

    The latest research indicates that the main way the new coronavirus spreads is through person-to-person contact in close quarters, Vox reports. "When you look at public transport, work spaces, restaurants—places where we're just trying to fit many people in a small confined space—respiratory viruses like those spaces," Muge Cevik, a physician and expert in virology at the University of St. Andrews, said.

    However, a variety of studies on influenza, rhinovirus, coronavirus, and other microbes have found that respiratory illnesses, including Covid-19, can still spread through contaminated surfaces. So how likely are you to catch Covid-19 from touching a surface?

    How the new coronavirus spreads from a surface

    Research has found the new coronavirus can last up to three days on plastic and metal surfaces and on cardboard for 24 hours. However, there are a lot of things that need to happen for a person to contract Covid-19 from touching a contaminated surface.

    First, a person must come in contact with enough of the virus to actually cause an infection. For example, to be infected with the influenza virus, millions of copies of the virus need to reach a person's face from a surface, but only a few thousand copies are needed when the virus goes directly into the lungs, the New York Times reports.

    If a person happens to touch a surface with large traces of the virus, they'd have to pick up enough of the virus and then touch their eyes, nose, or mouth—which is why public health experts say it's so important to frequently wash your hands and avoid touching your face.

    "There's a long chain of events that would need to happen for someone to become infected though contact with groceries, mail, takeout containers, or other surfaces," Julia Marcus, an infectious disease epidemiologist and assistant professor at Harvard Medical School, said. "The last step in that causal chain is touching your eyes, nose, or mouth with your contaminated hand, so the best way to make sure the chain is broken is washing your hands."

    While CDC's update may have caused some initial confusion, Erin Bromage, a comparative immunologist and biology professor at the University of Massachusetts, Dartmouth, explained that the agency was trying to make clear "that high touch surfaces like railings and doorknobs, elevator buttons are not the primary driver of the infection in the United States."

    However, Bromage added, "But it's still a bad idea to touch your face. If someone who is infectious coughs on their hand and shakes your hand and you rub your eyes—yes, you're infected. Someone's drinking from a glass, and you pick it up near the rim and later rub your eyes or mouth, you're infected" (Parker-Pope, "Well," New York Times, 5/28; Resnick, Vox, 5/22; Guarino/Achenbach, Washington Post, 5/21).

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