Outbreak investigation of food poisoning from Vibrio parahaemolyticus, in Nawa District, Nakhon Phanom Province, Thailand, August 2019

Abstract

Background: On 13 August 2019, Division of Epidemiology was notified from the Office of Disease Prevention and Control Region 8 Udon Thani, of 88 food poisoning cases in Nawa District, Nakhon Phanom Province. Most cases lived in villages no. 1, 2, 8 of Na-ngua Sub-district and reported consumption of steamed green mussels prior to illness from the 4 temples in the sub-district. The objectives were to verify diagnosis and outbreak, determine epidemiological characteristics of the cases, find the source of disease transmission and recommend control measures.
Methods: The investigation included medical record review of the sick persons, active case finding in the villages no. 1, 2, 8 of Na-ngua Sub-district and sample collection from the suspected cases, food handlers, suspected food, drinking water in the affected areas, and some raw seafood from the markets. Environmental investigation was also conducted in the area.
Results: Of 293 persons screened, 105 food poisoning cases (35.8%) were found without death. The highest attack rates were seen in persons aged ≥ 60 years old, in monks/novices, and in village no. 1. Clinical manifestations were watery/mucous bloody diarrhea or loose stool ≥ 3 times within 24 hours (100.0%), abdominal pain (89.5%), vomiting (60.0%). Of the 6 cases with rectal swab culture, 4 were positive for Vibrio parahaemolyticus. Most cases (86.7%) were clustered between 12 am of 12 August 2019 and 3 am of 13 August 2019. The case-control study revealed a significant association between consumption of steamed green mussels (odds ratio = 59.5, 95%CI 23.93–147.99). The steamed green mussels which were served in the 4 temples of Na-ngua Sub-district on 12 August 2019 were not well cooked. One of the 2 food handlers who steamed the green mussels was found to be infected with V. parahaemolyticus. Five of the 10 raw seafood samples collected were positive for V. parahaemolyticus.
Conclusions: This common-source outbreak of food poisoning might be caused by V. parahaemolyticus from consumption of not well steamed green mussels. Since raw seafood is frequently contaminated with this organism, it is essential to educate people to cook seafood adequately and encourage them to eat well-cooked seafood.