Three years after a large outbreak in university residence halls, cases of norovirus again are appearing in Madison and the University of Wisconsin.

The norovirus outbreaks have begun and are infecting those in densely populated areas and living spaces. The virus last largely affected student life in 2008, when many residents in UW dorms and fraternity and sorority houses fell ill.

The primary symptoms of norovirus include diarrhea, vomiting, trembling hands and other symptoms. According to Amanda Kita-Yarbro, head epidemiologist for Madison and Dane County Public Health, the virus often is mistaken for stomach flu.

Craig Roberts, an epidemiologist at University Health Services, said UHS sees enough norovirus cases to be called an outbreak in the dorms about once a year.

“It’s a very common infection, very contagious,” Roberts said. “It is easy to spread from person to person, especially when people live in close environments like residence halls or similar situations.”

He said the typical response to an outbreak in residence halls is to augment the cleaning process, particularly in doing extra cleaning in the restrooms, public areas and common spaces of the residence halls.

Additionally, Roberts said the real number of students affected by norovirus in the dorms is hard to know, as it is often suspected, but never confirmed. He said the same symptoms may also appear with other illnesses.

“It’s so common; it’s around all the time in the winter,” Roberts said. “We have a lot of it going around in southern Wisconsin this winter.”

She said an outbreak at Jefferson Middle School started around Feb. 16 and carried on throughout last week, although things seem better as of Feb. 27.

Kita-Yarbro said the virus is extremely common and very contagious. She said Madison has a “norovirus season” every year around this time.

The virus spreads via direct contact and ingestion, particularly when people touch an infected surface and go to eat or put their hands in their mouths. Additionally, Kita-Yarbro said the virus may be airborne in an area where someone vomits.

At Jefferson Middle School, Kita-Yarbro said Public Health has been working with the nursing staff to help curb the spread of the virus. She said Public Health consulted the staff on cleaning methods and testing for the virus.

The polling facility set up at The Jefferson, an independent living facility for retirement-age people, had to be shut down a couple of weeks ago when the virus was found to be circulating among residents, Kita-Yarbro said.

“They have nursing staff and infection control practitioners,” Kita-Yarbro said. “We consult with them on an as-needed basis.”

Additionally, she said that although there are not any more cases than usual in the city at this time, it is important to let people know how to protect against it.

Kita-Yarbro said if a person has symptoms of diarrhea or vomiting he or she should stay home for at least 48 hours after experiencing these symptoms, and should wash his or her hands often, in a different bathroom than others if possible, though this may be difficult in settings such as residence halls.

People who are not sick and have not been should also wash their hands often, especially before eating or putting their hands in or near their mouths.

“People not associated with a group or setting are also getting infected, but that’s not as common,” Kita-Yarbro said.