DETROIT -

The Michigan Department of Community Health says they've traced the norovirus outbreak at the Tough Mudder race to exposure on the actual course.

In a statement, MDCH said feedback from event attendees showed that the majority of ill individuals were likely exposed on the course itself, as the illness was highly associated with reports of mud or muddy water in the mouth. This indicates that contamination was likely introduced onto the course by an ill participant early in the event and persisted for the duration of the weekend.

Read back: Tough Mudder participants fall ill

The department began investigating after hundreds of people out of the more than 22,000 who participated in the late June event in Brooklyn, Mich., reported getting sick with nausea, vomiting, diarrhea, and abdominal cramps.

MDCH confirmed norovirus was to blame.

View: MDCH's release on norovirus at Tough Mudder

According to MDCH, norovirus is transmitted through touching virus-contaminated surfaces and objects, eating or drinking contaminated food, or by direct person-to-person contact.

It is highly transmittable and hand sanitizers are not effective against the virus.

Good personal hygiene, including frequent hand washing with warm, soapy water for 20 seconds is crucial to preventing the spread of the disease.

The Tough Mudder organization is working in partnership with MDCH ato identify measures to minimize the risk of a similar occurrence at future events.