Norovirus, a highly communicable stomach virus responsible for millions of cases of gastroenteritis annually, has been found in several outbreak locations throughout North Carolina.

Each year, the winter months throughout the country are marked by an increase in gastrointestinal distress. The culprit is often thought to be norovirus—a highly contagious type of stomach virus that can set off bouts of severe nausea, vomiting and diarrhea. According to CDC estimates, norovirus causes about 20 million cases of gastroenteritis—swelling of the linings of the stomach and/or intestines—each year in the United States alone, and there have been seven confirmed cases in North Carolina since this year’s virus season began.

This year, a particularly infectious strain of the virus, known as GII.4 Sydney, named after Sydney, Australia, where it was first discovered, has been the leading cause of norovirus outbreaks, said Dr. Cameron Wolfe, infectious disease specialist at Duke Medicine.

“The Sydney strain is a slight variation on a pre-existing norovirus strain,” Wolfe said. “In the same way that influenza can change from year to year, different versions of norovirus can change their makeup over time.”

Wolfe noted that the Sydney straom has greater infectivity than other norovirus strains. It is capable of infecting individuals quickly and easily, and it can take as few as 100 norovirus particles from a typical strain to infect a person, according to the North Carolina Department of Public Health.

The Sydney strain typically manifests with acute severe nausea, stomach cramps and diarrhea. These symptoms are typically mistaken for stomach flu, which makes identification of the illness difficult for medical professionals, Wolfe noted.

Although the illness’ symptoms can be debilitating, they are typically short-lived among healthy individuals, said Dr. David Mellinger, associate professor of pediatrics who also works in Student Health.

“[Norovirus] is a common cause of vomiting and diarrheal illness, so people come in feeling very sick, but it usually only lasts a day or two,” he said.

As such, Wolfe said few primary care doctors test specifically for norovirus. Instead, they simply treat the symptoms with fluid intake and rest.

To prevent norovirus infection, Mellinger said he advises students to wash their hands frequently and well. Because norovirus is one of a small percentage of viruses unaffected by alcohol-based hand sanitizers—commonly used brands such as Purell do not protect against .01 percent of viruses—Mellinger recommends the use of either dilute household bleach or hot water and soap to fully eliminate the virus.

Wolfe added that although Duke has yet to see any significant uptick in gastrointestinal disease, college dormitories are “a classic example” of a place with high transmissibility of norovirus.

“The courteous thing to do is, if you know you’re sick yourself, especially in a situation like in a dormitory, you should self-isolate, make sure you’re not sharing utensils or food with anyone around you, and wash your hands often,” he said.