An outbreak investigation of food poisoning in a temple fair, Tambon Pa Tum, Prao District, Chiang Mai, 27–30 March 2017

Abstract

Background: A food poisoning outbreak at a temple in Phrao District, Chiang Mai Province was notified on March 27th, 2017. There were 80 patients, of whom 50 patients were treated in Phrao Hospital and 15 patients were referred to 5 nearby hospitals. The first patient became ill with diarrhea, abdominal pain, and fever on March 25, 2017. The Joint Investigation Team from Office of Disease Prevention and Control region 1 and other SRRT investigated the outbreak during March 27th-30th, 2017 to determine epidemiological characteristics of the outbreak, to find the source of outbreak transmission and to recommend control measures.
Methods: Active case finding was conducted among people attending and eating foods in the temple fair during the outbreak by using snowball technique. A retrospective cohort study was conducted to determine the source of outbreak transmission. Data regarding the onset of symptoms, presenting features and history of food items consumed were collected. Food handlers were interviewed about food poisoning symptoms and food preparation process. Stool samples from the cases and suspected food specimens were collected for laboratory analysis.
Results: Of 256 people involved in this event, 105 cases were identified, giving an overall attack rate (AR) of 41.02%. None died in this outbreak. The highest attack rate was in children 0-4 years old. Most patients had fever (79.05%), abdominal pain (72.28%) and dyspnea (65.71%). Cases had onset during 0.30 pm on March 25th to 05.00 pm on March 28th, 2017. The incubation period was 9-45 hours (median 14 hours). Multivariate analysis showed the significant relationship between eating the dessert (Ruam-Mit) and the disease. People who ate RuamMit < 1 cup and ≥ 1 cups were likely to have illness 36.44 and 65.12 times respectively than those who did not. The result of multiplex real-time PCR could not really indicate either Shigella spp. or Enteroinvasive Escherichia coli (EIEC) in stool specimens. Roam-Mit samples were found to contain EIEC.
Conclusion: Outbreak of food poisoning in the temple fair at Phrao District, Chiang Mai Province, was caused by EIEC contaminated in Ruam-Mit. The disease surveillance after the outbreak showed no additional patients.