What’s the Risk of Catching Coronavirus From a Surface?

Fears about catching the coronavirus from contaminated surfaces have prompted many of us to spend the past few months wiping down groceries, leaving packages unopened and stressing about touching elevator buttons.

But what’s the real risk of catching Covid-19 from a germy surface or object?

The question has been on people’s minds lately, and there was some confusion after the Centers for Disease Control and Prevention made some edits to its website last week. Social media sites and some news outlets suggested the agency had downgraded its warnings and that surface transmission was no longer a worry.

“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,” the agency wrote. “But this isn’t thought to be the main way the virus spreads.”

So does this mean we can catch coronavirus from touching a doorknob? Catching a Frisbee? Sharing a casserole dish?

Next, you have to come along and touch the contaminated surface, pick up enough viable virus on your hands, and then touch your eyes, nose or mouth. If all goes well for the virus, you will get sick.

“There’s a long chain of events that would need to happen for someone to become infected through contact with groceries, mail, takeout containers or other surfaces,” said Julia Marcus, an infectious disease epidemiologist and assistant professor in the department of population medicine at Harvard Medical School. “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.”

Dr. Chudnovsky, a theoretical physicist whose research has focused on the spread of the airborne infection, said a similar pattern is likely to be true for the new coronavirus, but the exact numbers are not known.

“I believe the C.D.C. is right when it says that surface transmission is not a dominant one,” said Dr. Chudnovsky. “Surfaces frequently touched by a large number of people, like door handles, elevator buttons, etc., may play a more significant role in spreading the infection than objects touched incidentally, like food packages delivered to homes.”

The bottom line is that the best way to protect ourselves from coronavirus — whether it’s surface transmission or close human contact — is still social distancing, washing our hands, not touching our faces and wearing masks.

“Hand washing is important not only for fomite transmission, but also for person-to-person transmission,” said Dr. Daniel Winetsky, a postdoctoral fellow in the division of infectious diseases at Columbia University. “The respiratory droplets we produce when speaking, coughing and sneezing fall mostly onto our hands, and can fall onto other people’s hands if they are within six feet from us.”

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