Introduction:
We present the case of a large outbreak of gastroenteritis with a food and beverage premises as the source. This outbreak had more than 100 suspected cases although only a sample of these were tested and interviewed by Public Health.

Case description:
This investigation was prompted by several complaints of acute gastrointestinal illness made by members of the public to the Environmental Health service and the Food Safety Authority of Ireland. All complaints had a common exposure history and the majority had symptoms which developed within 48 hours of being in the premises. Initial investigations identified contaminated water and ice as the likely source of infection and a further rapid case/control study confirmed this. The premises were fully inspected by the local council and Environmental Health officers and the water supply was found to have extremely high levels of bacterial contamination. This was despite the fact that the water supply to the premises came from the local mains water supply and not from a private well. The premises in question did have a private well but water from this was only used for watering plants and washing outdoor equipment according to the business operator. Of the stool samples tested from affected patrons, five were positive for Norovirus, and none had evidence of bacterial infection.

Discussion:
This outbreak presented a particular challenge to the Health Protection team as due to the scale of the outbreak it was impossible to interview and test all of those affected. In addition, despite only isolating Norovirus from the stool samples, it seems improbable that the levels of bacterial contamination seen in the water samples would not have been responsible for much of the illness caused.