Apparently fairly low, according to an article in The Washington Post by Joseph Allen, assistant professor of exposure and assessment science at Harvard University.
First, disease transmission from inanimate surfaces is real, so I don’t want to minimize that. It’s something we have known for a long time; as early as the 1500s, infected surfaces were thought of as “seeds of disease,” able to transfer disease from one person to another.
In that new NEJM study, here’s the finding that is grabbing headlines: The coronavirus that causes covid-19 “was detectable . . . up to four hours on copper, up to 24 hours on cardboard and up to two to three days on plastic and stainless steel.”
. . .
Yes, the virus can be detected on some surfaces for up to a day, but the reality is that the levels drop off quickly. For example, the article shows that the virus’s half-life on stainless steel and plastic was 5.6 hours and 6.8 hours, respectively.
. . .
You can leave that cardboard package at your door for a few hours — or bring it inside and leave it right inside your door, then wash your hands again. If you’re still concerned there was any virus on the package, you could wipe down the exterior with a disinfectant, or open it outdoors and put the packaging in the recycling can. (Then wash your hands again.)
What about going to the grocery store? The same approach applies.
Shop when you need to (keeping six feet from other customers) and load items into your cart or basket. Keep your hands away from your face while shopping, and wash them as soon as you’re home. Put away your groceries, and then wash your hands again. If you wait even a few hours before using anything you just purchased, most of the virus that was on any package will be significantly reduced. If you need to use something immediately, and want to take extra precautions, wipe the package down with a disinfectant. Last, wash all fruits and vegetables as you normally would.