A number of Stevens County towns are in the middle of a norovirus outbreak, the Northeast Tri-County Health District said Saturday.

Kettle Falls, Colville and Chewelah are seeing cases of the disease, a highly contagious virus that causes vomiting and diarrhea.

Three people in the county have confirmed norovirus cases, and about 35 have sought medical care for norovirus-like symptoms, said Matt Schanz, the health district administrator.

Most people recover from the virus without needing medical care, so the true number of cases is likely higher, he said.

Norovirus can survive on surfaces for weeks, and not all disinfectants will kill it, the health district said in a news release. It tends to spread quickly in closed environments like cruise ships, nursing homes and college dormitories.

Stevens County has seen cases in nursing homes, hospitals and a few in schools, though so far the illness has not caused an unusual number of absences, Schanz said.

People typically show symptoms within 12 to 48 hours of exposure to the virus and will usually be sick for one to three days. People remain contagious for 48 hours after recovery.

Spokane County typically has about one active norovirus outbreak a week this time of year, Spokane Regional Health District spokeswoman Kim Papich said.

Last week, the district recorded two active outbreaks, one at Manor Care Health Services, a nursing home, and Lakeland Village, a care facility for people with disabilities.

Regular handwashing with soap and water is more effective than hand sanitizer at killing the virus, according to the Tri-County Health District. Infected people should not prepare food while they have norovirus, and food service workers who are sick should not return to work until they’ve felt better for three days.