Outbreak investigation of food poisoning due to vibrio parahaemolyticus among hospital workers participating in a strategic planning meeting

Abstract

Objective : To identify the source of food poisoning outbreak in the meeting and
formulate recommendations to prevent further outbreaks.
Methods : 138 hospital workers (HWs) participated in a strategic planning meeting
during July 25-26, 2011 or one day and some developed diarrhea. Accordingly
social medicine department launched a retrospective investigation
through self-administered questionnaires. Two food handlers (FHs) were
interviewed about food preparation. Rectal swab of the HWs and the FHs
were examined to identify pathogens of food borne diseases. A food
poisoning case was defined as a HW who participated in the meeting and
had one of following symptoms: at least 3 loose stools, one watery stool,
one mucous stool per day or two of following symptoms: less than three
loose stools per day, abdominal pain, nausea, vomiting, headache or fever.
Results : Of 138 HWs, 38 (27.5 percent) met the case definition. Most common symptoms
were watery diarrhea (76.3 percent), loose stool (63.2 percent) and
abdominal pain (55.3 percent). Regarding an epidemic curve, the first and
the last case were found on July 26 and 29, respectively. The maximum
number of cases was reported on July 27 during 0.01-12.00 a.m. The multivariable
analysis demonstrated that steamed crayfish is significantly
associated with food poisoning (Adjusted odds ratio = 8.4, 95 percent
confidence interval = 1.1-63.5). Of 13 cases, three (23.1 percent) had positive
rectal swab cultures for Vibrio parahaemolyticus; however, all FHs had
negative rectal swab cultures and clinical symptoms of food poisoning.
Interviews with responsible FHs regarding cooking processes suggested
inadequately cooked seafood might cause the outbreak, especially when
large amount of seafood were prepared.
Conclusion : This was a confirmed outbreak of Vibrio parahaemolyticus. The investigation
suggested that contaminated crayfish was a source of the outbreak
because of unhygienic cooking processes. To prevent future outbreaks,
education programs on proper sanitation and cooking should be provided
for FHs and the seafood preparation and cooking should be concerned in
the next meeting.
Keywords : outbreak investigation, foodpoisoning, Vibrio parahaemolyticus