Chapel Hill, N.C. — Health departments across North Carolina have reported norovirus outbreaks in recent weeks, prompting state public health officials to issue an alert Tuesday.

The state Division of Public Health doesn't track norovirus, so officials don't have specific numbers of people sickened by the gastro-intestinal bugs. They said, however, that eight counties have reported outbreaks, including Wake, Orange, Alamance and Pitt.

"It's explosive," said Dr. David Weber, an infectious disease specialist at the Gillings School of Global Public Health at the University of North Carolina at Chapel Hill. "It takes only about one to two days, at most three days, after being exposed before you would develop diarrhea. So that, by the time you start seeing cases, and it's highly contagious, you could have an outbreak."

The Orange County Health Department has seen two outbreaks since Christmas, said Susan Rankin, a registered nurse in the department. Both were at workplaces, and one involved 55 people while the other involved 20, she said.

Weber said he's unaware of any patients at UNC Hospitals for norovirus, but he said most people likely wouldn't be hospitalized for the illness. Physicians are most concerned when young children and the elderly contract norovirus, he said.

North Carolina usually sees an increase in norovirus cases between October and March, but health officials said they've seen a noticeable upswing in the past month.

”It is more common in the winter ... because it’s a fairly hardy virus, so it will live on environmental surfaces for days to weeks," Weber said, "and of course, we are packed in more at home. We are less outside, so it does tend to occur more in the winter.”

The best prevention is frequent hand washing, he said, adding that alcohol-based hand sanitizers don't work against the virus.

Symptoms include nausea, vomiting, diarrhea and stomach cramps. They usually last one or two days, but people are contagious for at least three days after they recover.

Norovirus is easily spread by touching a contaminated surface or by eating food prepared by someone who's sick, officials said. Weber urged people who feel ill to stay home to avoid spreading the illness, and said people should use bleach-based cleaners to wipe down desks, counters and other surfaces.