Norovirus is the culprit that recently sickened dozens of University of Michigan sorority members, the Washtenaw County Health Department confirmed Wednesday.

And this is the time of year those outbreaks tend to happen due to people spending more time indoors and more time together at festive gatherings, said Susan Cerniglia, spokeswoman for the Washtenaw County Public Health Department.

The Ann Arbor police and fire departments responded to the University of Michigan chapter of the Delta Delta Delta sorority after several dozen women reportedly fell ill following a communal meal.

Juliana Keeping | AnnArbor.com

The Ann Arbor police and fire departments responded to the Delta Delta Delta sorority house at 718 Tappan Ave. at 10 p.m. Saturday, Oct. 23 after a caller said 37 women were ill. According to the department, women at that address and in the 800 block of Hill Street were vomiting and not feeling well. They had eaten together at a communal meal the day before.

The health department began its investigation into the incident last week, taking food histories of those who became ill versus those who did not and testing stool samples, which were sent to a Michigan Department of Community Health lab.

The results came in Wednesday. “We have confirmed it’s norovirus,” Cerniglia said.

The exact cause of the virus isn't known. It’s easy to catch the bug through airborne particles, contaminated food or surfaces.

A spoon at a buffet can spread the virus, for example, said Laura Bauman, the Health Department’s epidemiologist..

Noroviruses are among the numerous causes of food poisoning. The group of viruses cause gastroenteritis, an inflammation of the lining of the stomach and intestines, according to the Centers for Disease Control.

Symptoms typically include nausea, stomach cramping, vomiting and diarrhea. 
 Symptoms appear 24 to 48 hours after ingestion through contaminated food or liquids, surfaces or objects or other contact with someone who is ill.



Bauman said around six outbreaks occur per year linked to noroviruses in Washtenaw County. An outbreak is more typically in the 10-to-20-person range, though local norovirus outbreaks have sickened hundreds of local people at once.

Juliana Keeping is a health and environment reporter for AnnArbor.com. Reach her at julianakeeping@annarbor.com or 734-623-2528. Follow Juliana Keeping on Twitter