Abstract
An acute gastroenteritis (AG) outbreak occurred among participants in an obstacle race in France in the summer of 2015. An investigation in two phases was conducted to identify the source of infection and document the extent of the outbreak. First, a message on a social media website asked racers to report any symptoms by email to the Regional Health Agency of Provence-Alpes-Côte d'Azur. Second, a retrospective cross-sectional study was conducted through an interactive questionnaire for all participants, followed by an analytical study of potential risks factors. Of 8,229 persons registered, 1,264 adults reported AG resolved within 48 hours. Of adults who reported AG, 866 met the case definition. Age group, departure time and ingestion of mud were associated with AG. Twenty stool specimens tested negative for bacteria. All four stool samples tested for viruses were positive for norovirus genogroup I and genotype 2. No indicator bacteria for faecal contamination were found in drinking water but muddy water of ponds tested positive. The outbreak was possibly caused by human-to-human transmission of a norovirus introduced by one or more persons and transmitted through contaminated mud. Risks related to similar races should be assessed and recommendations be proposed to raise awareness among health authorities and organisers.
Highlights
Obstacle races are extreme sport events, combining a difficult path and obstacles
ARS PACA and Cire Sud sent a message on a social media website informing the participants of the obstacle race that an investigation was conducted and asked them to report any recent or current gastrointestinal illness by email to a dedicated address of ARS
We provided recommendations on measures to prevent secondary spread during a press conference organised on 22 June, through a weekly report of the Cire Sud, on the ARS PACA website, and we posted prevention messages on a social media website
Summary
On a distance of several kilometres, obstacles such as walls, nets, ice baths, barbed wires, mud mounds, tunnel crawls, dark rooms, live electrical wires are positioned along the path. These sport events have been growing in popularity during the last years. In the United Kingdom (UK), a case of Escherichia coli 0157:H7 after a mountain-bike race has been described [4]. Other races, such as triathlons, have been linked to cases of leptospirosis, for example on the Reunion Island in 2013 [8]. Skin wounds caused by Aeromonas hydrophila, after a ‘mud football’ have been described in Australia in 2002 [9]
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