Outbreak Investigation of Food Poisoning in a School, Mueang district, Phitsanuloke, May 2017

Abstract

Background: On May 9 , 2017 a primary care unit in Mueang Phitsanuloke district was informed by a teacher that there were 59 students in orientation camp presenting with nausea, vomiting, abdominal pain and watery diarrhea. The surveillance and rapid response team conducted the investigation during May 9-11, 2017. The investigation aimed at confirming diagnosis and outbreak, characterizing occurrence and distribution of the outbreak epidemiologically, and identifying causative agent and factors contributing to the outbreak with the ultimate goals of controlling and preventing the outbreak.
Methods: Descriptive study was conducted among all camp participants and outsiders who had eaten foods of this camp on May 9, 2017. A case was defined as a person with at least one of the following symptoms: nausea, vomiting, abdominal pain and diarrhea. The analytic study (Retrospective cohort study) was conducted to identify the association between various foods items and illness.
Results: There were 123 camp participants (106 students, 15 teachers, 2 janitors) and one outsider who had eaten a school’s food item. Eighty-four patients were found including eighty-three camp participants (attack rate=67.48%) and one outsider. The median of age for the patients was 13 years old (min=11, max=67). Incubation periods ranged from 1.5 to 3.5 hours (median=3.5 hours). Vomiting and nausea were two highest predominant symptoms with the proportion of 84.52% and 77.38% respectively. More than half of patients (55.95%) were hospitalized. The illness was strongly associated with eating boiled chicken (OR = 13.72, 95% CI 1.42-132.32, pvalue =0.02 3 ). Amount of boiled chicken rice consumption also had positive linear correlation with the illness. Staphylococcus aureus were isolated in chicken rice. Cooked food (boiled chicken) was prepared with bare hands and kept in room temperature more than 8.5 hours before serving.
Conclusions: Staphylococcus aureus contaminated in boiled chicken by improper food handling was the most likely causative agent. Prevention and control measures were recommended including avoiding keeping food at the room temperature for a long time before serving. Health education on food sanitation, personal hygiene and ways to combat diarrhea was provided to all participants.