Introduction: Raw seafood consumption has frequently been linked to gastroenteritis and Norovirus is a common cause. In February and March 2010, there was an increase cases of gastroenteritis on the remote island of Agios Efstratios in the Northern Aegean Sea, Greece. A massive increase in seafood consumption associated with a religious festival a few days prior to the outbreak suggested seafood as the vehicle of transmission.
Methods: An outbreak investigation team visited the island in order to document the outbreak and find epidemiological evidence for its source. The whole island was used as a cohort in the retrospective cohort study that was conducted.
Results: Sixty-four of the 181 participants reported having had symptoms of gastroenteritis, of which 34 were considered primary cases. People who consumed any raw seafood imported to the island were 21.5 times (95% CI: 8.95-51.8) more likely to develop symptoms of gastroenteritis in the 72 hours following exposure. Consumption of local seafood was not found to be a risk factor.
Conclusion: Despite the lack of laboratory evidence, all four Kaplan's criteria were met and the outbreak was thought to have been caused by Norovirus. The outbreak investigation demonstrates epidemiological methods for use in a remote setting, where the means for laboratory and environmental investigation may be absent or limited.