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

Abstract 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)/100 ml of total coliforms and five MPN/100 ml 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.