There’s a lot of hepatitis A going around in Southern California. With an outbreak going through the homeless population in a couple of counties and potential exposure of fruit cart patrons, there’s lots of paranoia.

The San Diego Tribune asks, can you get hep A from a door knob (this outbreak’s version of a toilet seat can give you HIV). My friend, colleague, and virologist extraordinaire, Lee-Ann Jaykus answers the call:

Lee-Ann Jaykus, a microbiologist at North Carolina State University who specializes in hepatitis and other types of food-borne illness, said that, while it is definitely possible for this bug to linger on a surface — maybe for weeks — it’s not likely.

She noted that only one activity is known to spread a hepatitis A infection: Accidentally ingesting a tiny amount of an infected person’s feces.

Even though this microbe is tough enough to live on surfaces for extended periods, it would take quite a large amount of material, she said, to actually have a transfer occur.
“It’s not impossible, but the chances are very slim. You would need people walking around with a lot of poop on their hands all of the time to be causing a problem in the general population,” Jaykus said.

Research shows that the chance of transference decreases with each thing that person touches after their hands are contaminated, she said. And dry surfaces tend to be less prone to collecting and holding substances than wet surfaces.

So, an infected food service worker who does not adequately wash his or her hands after going to the bathroom is more likely to transfer the illness to a moist, cold piece of lettuce while building your burger than a homeless person is to leave behind a significant contamination on the door handle of a downtown restaurant.

In all cases, Jaykus added, the bit of bad stuff would have to make it into your mouth. So, in the context of public transportation, just don’t lick anything at your local bus stop and wash your hands before putting them near your mouth. You should be just fine.