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Norovirus Outbreak Investigation Results Indicate Exposure Occurred on Course


LANSING – Epidemiologists with the Michigan Department of Community Health (MDCH), in cooperation with the Lenawee County Health Department (LCHD), investigated an infectious disease outbreak associated with the Tough Mudder event held in Brooklyn, Mich. on June 29-30, 2013. The event included more than 22,000 participants and spectators. Following the event, MDCH and LCHD received many reports of gastrointestinal illnesses, which were determined by the MDCH Bureau of Laboratories to be caused by norovirus. All participants and spectators who became ill from the event should now be recovered.

Feedback from event attendees shows that the majority of ill individuals were likely exposed on the course itself, as illness was highly associated with reports of mud or muddy water in the mouth. Due to the size of the event, participants started the course in waves over several hours on Saturday and Sunday. The frequency of reported illness increased dramatically in participants starting in the first several hours on Saturday and remained steady throughout the rest of the weekend. 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.

Symptoms of norovirus infection include nausea, vomiting, diarrhea, and abdominal cramps, typically lasting one to two days. Transmission of norovirus can occur when someone touches contaminated surfaces and then touches his or her mouth. It is also spread by consuming contaminated food or drinks or through close personal contact with an infected person. Those ill with norovirus can spread this highly infectious virus through vomiting and diarrhea for days or weeks after symptoms subside.

Good personal hygiene, including frequent hand washing with warm, soapy water for at least 20 seconds, is an effective way to prevent the spread of the disease. Hand sanitizers alone are ineffective at reducing norovirus transmission. Additionally, surfaces should be frequently disinfected with chlorine bleach solution, and ill individuals should avoid preparing food for others. Public health agencies and the Tough Mudder organization have reached out to participants with this prevention message to minimize the risk of secondary transmission of the infection and to further investigate the outbreak.

The Tough Mudder organization is working in partnership with MDCH and LCHD to identify measures to minimize the risk of a similar occurrence at future events. Recognizing the risk of transmission from ill participants at this type of event, public health and Tough Mudder officials are collaborating to develop methods of communicating this risk to future participants and promoting voluntary exclusion of symptomatic individuals from participation. Tough Mudder is also developing strategies and policies to ensure the health and safety of participants in future events.

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