Detection and management of a norovirus gastroenteritis outbreak, Special Olympics World Summer Games, Greece, June 2011

The 2011 Special Olympics Summer Games were hosted in Greece, from 25 June to 4 July. A syndromic surveillance system was implemented for the needs of the Games. On 26 June a cluster of viral gastroenteritis cases among the members of the British delegation was detected. The delegation had arrived in Athens on 24 June from the island where they had been on holidays since 20 June. Control measures were implemented. Descriptive epidemiological data were gathered and a 1:1 case-control study was conducted. Controls were selected via simple random sampling, using a list of the British delegation members and a random number table. Data showed that this was a common point source outbreak. Cases were exposed on 24 June during their return to Athens. The only recognised statistically significant risk factor was a prior contact with a symptomatic case (OR=14.6, 95% CI 1.81-118.1). One specific case that reported vomiting during the trip was identified as the probable source of the outbreak. Two stool samples were positive for norovirus. Control measures resulted to the restriction of the outbreak and no cases were notified among the members of the other delegations. The syndromic surveillance system detected the outbreak on the first day of the Games. The investigation revealed the lack of laboratory capacity for virological testing of stool samples and the effectiveness of syndromic surveillance to identify the outbreak. Key words: