Norovirus outbreak of probable waterborne transmission with high attack rate in a Guatemalan resort.

Background: In February 2009, a group of Guatemalan school children developed acute gastroenteritis (AGE) after participating in a school excursion.

Objectives: We conducted a retrospective cohort investigation to characterize the outbreak and guide control measures.

Study Design: A case was defined as an illness with onset of diarrhea or vomiting during February 25-March 5, 2009. Participants were interviewed using a standardized questionnaire, and stool specimens were collected. We inspected the excursion site and tested water samples for total coliforms and Escherichia coli.

Results: We identified 119 excursion participants, of which 92 (77%) had been ill. Fifty-six (62%) patients sought care for their illness, and three (3%) were hospitalized. Eighteen (90%) of the 20 specimens from ill children tested positive for norovirus. Among these, 16 (89%) were of the genogroup I (GI.7) and two (11%) were genogroup II (GII.12 and GII.17). One (8%) of the 12 food handlers had norovirus (GI.7). Drinking water samples had 146 most probable numbers (MPN)/100ml of total coliforms and five MPN/100ml of E. coli.

Conclusion: We describe the first laboratory-confirmed norovirus outbreak in Guatemala. The high illness attack rate, detection of multiple norovirus strains in sick persons, and presence of fecal contamination of drinking water indicate likely waterborne transmission.