Outbreak of viral gastroenteritis due to a contaminated well. International consequences.

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.

Secular trends in hepatitis A virus infection among Alaska Natives.

To assess the epidemiologic characteristics of the population susceptible to hepatitis A virus (HAV) infection and determine the natural history of infection, a retrospective survey was done using banked serum specimens. A random sample of 4030 Alaska Natives statewide was selected, stratified by year of birth and community of residence. Overall, 1988 serum samples (49.3%) tested positive for antibody to HAV (anti-HAV). Past HAV infection was strongly age-related, increasing from 7% in persons born since 1975 to 85% among persons born before 1945. Prevalence of infection also varied between regions. In small communities, a clear demarcation typically existed between previously infected older persons and younger anti-HAV-negative persons. This indicated that village-wide outbreaks of HAV infection have been the norm and appear to be dependent on the presence of a young susceptible population. Widespread vaccination with hepatitis A vaccine to maintain a high proportion of young anti-HAV-positive persons may be successful in preventing future epidemics.

Epidemiologic surveillance of enteric diseases in Alaska--value of case investigation.

Patients infected by Salmonella, Shigella, Giardia, Campylobacter, Yersinia, and Hepatitis A virus were interviewed during a 15-month period to evaluate the benefit of intensive follow-up, to assess the proportion of cases who had contact with children less than four years of age, and to determine risk factors. Of 746 reported infections, we interviewed 345 patients (46%) and identified 199 other ill people. Follow-up of sporadic, passively reported cases required considerable resources, but no large outbreaks were uncovered. Investigation of patients [N = 103 (43%)] who had contact with children less than four years of age, or children who attended daycare centers often resulted in identification of additional illness, especially for cases of giardiasis. Primary health care providers can play a key role in reducing enteric disease by increasing efforts to identify illness among daycare and family contacts of their patients.