I’m unclear on fomites. I’ve read that transmission through touch is low because a particular series of events has to happen for the virus to be transmitted this way, but in a NYTimes survey of epidemiologists, a surprising percentage take precautions when handling their mail. I was sanitizing all packaged groceries until a month ago when I read that there’s likely no need to, but with the current surge where I live (Austin), I’m wondering if I should start again and be more cautious regarding other fomites.
Alison Bernstein, Ph.D.:
Fomites are inanimate objects that may transmit a virus, such as a doorknob. If a sick person touches a doorknob they may place viral particles onto it. Then, a healthy person could touch the doorknob and potentially transfer the virus to themselves. For transfer to occur, the virus needs to be able to survive for some time on the surface.
Several studies have examined how long SARS-CoV-2 can survive on objects. Depending on what the surface is - plastic, cardboard, metal - we know that RNA from the virus can last between a few hours and a few days. What we don’t know is whether this means there is infectious virus present and if that is enough to infect you. So it is possible to transmit Covid-19 through a fomite, but this will depend on how much virus is present and how much time it has been there.
A good precaution that gets around all the uncertainty about how long SARS-CoV2 can survive on surfaces is to wash your hands well after coming into contact with something that may have been contaminated.
Chris Kemp, M.S.:
Fomites are inanimate objects that can become contaminated with virus, so think: elevator buttons, door handles, etc. The field is still undecided on whether fomites are a major source of infection, but several recent papers do still consider them a possible secondary source of infection, far behind the much likelier route of airborne transmission. According to the CDC, the virus generally does not survive well on paper or cardboard. It lasts longest on steel but even then, its half-life on steel is around 5 hours or so. Short story: you're not likely to become infected from mail or groceries, and even less likely if you can leave them in a little quarantine spot for a few hours, or a day. For perishables, wipe them down if it makes you feel happier.