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BACKGROUND: Norovirus is the most common cause of acute gastroenteritis in the United States. Each year, it causes 19–21 million illnesses and contributes to 56,000–71,000 hospitalizations and 570–800 deaths. On July 10, 2014, Flathead City-County Health Department began receiving complaints of acute vomiting and diarrhea from staff and guests of Lodge A near Glacier National Park. Public health authorities visited Lodge A to identify risk factors for illness and recommend control measures.
METHODS: The local health department conducted case-finding and interviewed Lodge staff and guests. A case was defined as someone who had exposure to Lodge A during July 2–24 and illness onset ≤2 days following their last exposure, and either a) nausea and vomiting (clinical), or b) stool sample that tested PCR-positive for Norovirus GII (confirmed). An environmental investigation with laboratory testing of water samples was performed.
RESULTS: Sixty-four persons met the clinical and two met the confirmed case definitions, including 16 staff and 50 guests. Guests resided in 11 different states. Of the 50 guests, 46 (92%) became ill 1–3 days after arrival and none reported illness onset before arriving at Lodge A. Two stool specimens tested positive for norovirus GII.4 Sydney. Environmental control measures were initiated based on presumed person-to-person transmission, but additional cases were identified and alternative transmission routes were considered. The lodge was supplied by three wells; well A (drilled in 1974) supplied the main lodge and adjacent cabins, and wells B (2007) and C (2011) supplied additional cabins on separate systems. Water sampled from well A tested positive for Escherichia coli and norovirus GII.4 Sydney, wells B and C tested negative. Well A was disconnected and continuous chlorination was performed on the distribution systems for 10 days. The water distribution system was converted to a public water supply, thus ensuring regular monitoring and regulatory requirements. No new cases were reported.
CONCLUSIONS: Environmental findings confirmed well A was the source of this outbreak and identification of cases ceased once well A was taken offline. This investigation highlights the importance of a collaborative relationship among epidemiologic, environmental health, and laboratory professionals. Well-water testing should be considered when investigating outbreaks at facilities with aging water distribution systems.