A norovirus at the Pyeongchang Olympics means athletes might have more to worry about than just going for the gold.
More than 100 people have come down with the dreaded stomach bug, and South Korean Olympic organizers quarantined more than 1,000 workers after some tested positive for it.
The organizers called in police officers to take over from the quarantined workers after some tested positive for the norovirus, which causes nausea, vomiting and diarrhea.
WATCH: Stomach Virus Creates Headache for Olympic Officials
Dr. Cynthia Sears, an infectious disease expert at the Johns Hopkins School of Medicine, spoke to VOA by Skype.
"Norovirus is a virus that's exceptionally contagious. It can be spread by simply touching surfaces," she said.
Norovirus can survive for days or even weeks on a variety of surfaces. And, Sears says, it only takes a small amount of the virus to infect someone.
"It can be spread by vomiting because it can aerosolize to some extent. People can pick up enough that way,” she said. “It can be spread through the stool (fecal matter) if you accidentally get a little bit of feces on something."
The virus spreads quickly between people, especially in close quarters like cruise ships and nursing homes. It can spread wherever there are crowds.
The norovirus can also be passed on through contaminated food and water, if the person handling it has the virus, or gets fecal matter on the food or in a drink.
Symptoms normally last for a few days, but afterward, the sickness causes fatigue.
The antidote is cleanliness. If food preparation surfaces are disinfected and the food is cooked thoroughly, the virus's ability to survive is reduced.
The best defense is lots of handwashing and disinfecting any surfaces that might be contaminated, especially kitchens and bathrooms, and keeping your fingers away from your face.