Outbreak of Viral Gastroenteritis Due to a Contaminated Well

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Abstract
Context. —Small round-structured viruses (SRSVs) are known to cause viral gastroenteritis, but until now have not been confirmed in the implicated vehicle in outbreaks. Objective. —Investigation of a gastroenteritis outbreak. Design. —After applying epidemiologic methods to locate the outbreak source, we conducted environmental and laboratory investigations to elucidate the cause. Setting. —Tourists traveling by bus through Alaska and the Yukon Territory of Canada. Participants. —Staff of a restaurant at a business complex implicated as the outbreak source, convenience sample of persons on buses that had stopped there, and bus employees. Main Outcome Measures. —Odds ratios (ORs) for illness associated with exposures. Water samples from the restaurant and stool specimens from tourists and restaurant staff were examined by nucleic acid amplification using reverse transcription polymerase chain reaction and sequencing of viral amplification products. Results. —The itineraries of groups of tourists manifesting vomiting or diarrhea were traced back to a restaurant where buses had stopped 33 to 36 hours previously. Water consumption was associated with illness (OR, 5.3; 95% confidence interval [CI], 2.3-12.6). Eighteen of 26 employees of the business complex were ill; although not the index case, an employee ill shortly before the outbreak lived in a building connected to a septic pit, which was found to contaminate the well supplying the restaurant's water. Genotype 2/P2B SRSV was identified in stool specimens of 2 tourists and 1 restaurant employee. Stools and water samples yielded identical amplification product sequences. Conclusions. —The investigation documented SRSVs in a vehicle epidemiologically linked to a gastroenteritis outbreak. The findings demonstrate the power of molecular detection and identification and underscore the importance of fundamental public health practices such as restaurant inspection, assurance of a safe water supply, and disease surveillance.