The virus causes 20 million cases of gastrointestinal illness
in the United States each year, according to the Centers for Disease Control and Prevention, and it spreads easily in any area of close contact. So while stories of sick cruise ship passengers
are widely reported, cruise ship outbreaks represent less than 1% of all norovirus outbreaks, said Dr. Aron Hall, an epidemiologist in the CDC's division of viral illnesses.
Another vacation spot this virus can lurk
is tour buses. In August 2014, a survey of bus drivers in Yellowstone National Park
revealed that five buses were carrying passengers who had diarrhea or vomiting -- both symptoms of norovirus. One of the buses had 10 sick passengers.
Results of the survey helped fight the disease. Once the patients were identified, bus drivers were able to clean the buses and stop the virus from spreading. And when the sick passengers checked into their hotel, employees placed all of them in the same area.
The workers knew to take precautions while cleaning so they wouldn't spread the virus or become sick themselves. The hotel also limited the ability of the sick guests to spread their germs by arranging for room service and other services to go to them so they wouldn't have to leave.
Cara Cherry, an epidemic intelligence officer with the CDC, who is assigned to the National Park Service, developed the tour bus surveillance program. "By knowing someone is sick, we can increase steps to prevent further spread," she told CNN.
The surveillance was done last August, but this summer, it began in May. Cherry said that so far, no buses with multiple ill passengers have been found. She hopes to expand the program to other national parks and perhaps partner with the tour bus industry, in the interest of keeping people healthy and enjoying their vacation.
Care facilities and food handling
The norovirus also lurks in nursing homes and other long-term care facilities, where daily group activities, shared dining rooms and visitors from outside provide countless opportunities for it to spread.
"It's a perfect tinder box to spread rampantly," Hall said, adding that most norovirus deaths occur in such facilities, in part because if residents become infected, they are more likely to succumb to illness. That's why, in nursing homes especially, disinfecting is crucial on surfaces such as doorknobs, bed rails and bathrooms.
But close quarters aren't always to blame when it comes to norovirus. It's the leading cause of all foodborne disease outbreaks in the United States linked to restaurants and food services, accounting for half of all of food-related outbreaks in which the cause is identified. That means norovirus is to blame for more foodborne outbreaks than salmonella, E. coli, listeria, and other causes combined. There are an estimated 200 to 400 foodborne norovirus outbreaks per year.
The easiest way to keep norovirus from entering your gut through your mouth is by cooking food thoroughly. However, the bigger challenge is with raw and handled foods such as salads and sandwiches, which are more often to blame for these outbreaks.
Hall said that most commonly, a food worker with the virus on his or her hands passes it on to food that is eaten by someone else. The best way to prevent this is easy: "If we could get everyone to wash their hands, we would have far less norovirus and other infections," he said.
But foods can be contaminated before they get to the kitchen. Irrigation water has been the source of some outbreaks of this hearty virus, which can stick around for weeks at room temperature. In groundwater or dark environments, it can survive for months.
It's also important to isolate those who are infected, who should stay home from work, shouldn't prepare food and shouldn't take care of others, Hall said. "People can shed the virus even after they've recovered, so stay isolated for at least 24 hours after symptoms resolve," he recommended.