Just consider: one simple sneeze can produce as many as 40,000 droplets, some of which rocket out at speeds greater than 200 miles per hour.
And flu spreads by both direct and indirect contact. So touch something contaminated and you can get the flu.
Computer keyboards easily spread germs, so do telephones and door handles.
We stopped by the Boise Airport where people we talked to had their own worst thing to touch for germs.
"Since I'm at an airport, I'd say it's on the airplane itself," said Jesse Gonzales of Salt Lake City. "Those trays that fold up and down on the back of the seats can be really disgusting."
"The remote control for the television at the hotel room. That's probably the germiest thing you can touch," said Andy Holland of Portland. "those things really gross me out."
"Probably just shaking somebody's hand," said Dayna Carter of Ontario.
According to a new survey, one of the "germiest" things you can touch is the handrail on an escalators.
But the AARP says restaurant menus are the "germiest" things you can touch, followed by those restaurant lemon wedges and condiment dispensers.
Lemon wedges? Who knew?
Hand sanitizer is a good idea but doctors say your best -- and cheapest -- defense is good old-fashioned hand washing.