Outbreak investigation of acute diarrhea caused by norovirus in 5 schools in Phuket municipality, Phuket Province, Thailand, June 2023
DOI:
https://doi.org/10.59096/wesr.v55i7.1269Keywords:
outbreak, acute diarrhea, norovirus, school, Phuket provinceAbstract
Background: On 11 June 2023, the investigation team was notified from Division of Epidemiology that there were greatly reported cases of acute diarrhea in schools of Phuket province, where the cases were continuously high from the end of 2022. The team investigated the outbreak during 12–18 June 2023 to confirm diagnosis and outbreak, describe epidemiological characteristics of outbreak, identify risk factors and source of infection, and recommend preventive and control measures.
Methods: The investigation included active case finding in 5 schools in Phuket municipality, who had onset of the disease during 1–18 June 2023 by online questionnaire. Rectal swabs were collected from patients with present symptoms and environmental samples were collected from suspected sources for laboratory diagnosis. A retrospective cohort study was conducted to identify risk factors and source of infection. An environmental investigation was conducted in school A where the highest number of cases were found.
Results: A total of 214 suspected cases were detected in these 5 schools, giving the attack rate of 2.58%. Norovirus GII was identified in 4 of the 6 cases examined. None died in this outbreak. Clinical manifestations were abdominal pain (96.73%), loose stool (85.51%), vomiting (82.24%), and fever (52.34%). The cases were found to peak on 7–8 June 2023. Factors significantly (p < 0.05) associated with the disease were existence of ill family members (adj RR = 2.04), having drinks with ice at the shops nearby the school (adj RR = 1.89), having drinks with ice at the school shop (adj RR = 1.47), consuming foods purchased from the market for breakfast (adj RR = 1.35), and sharing a container/spoon/glass with others (adj RR = 1.29). Probable contamination with norovirus GII was reported from one sample of piped water used for the plants and coliform bacteria were found in swabs from buttons of drinking water dispensers in school A.
Discussions and Conclusion: Clinical manifestations of the cases and viral confirmation in rectal swabs suggested this outbreak might be caused by norovirus. However, the source of infection could not be identified. The disease might spread for some period of time in the community, and then by person–to–person transmission. Another possible mode of transmission might be having contaminated drinks with ice. The outbreak curtailed within 2 weeks after preventive and control measures.
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