On Thursday, 1 June 2006 at about 11:45 am, many workers while they were eating lunch inside the company restaurant at Al-Jubail Industrial City, started to develop dizziness, nausea, and vomiting. Most of the patients developed the symptoms within 5 - 15 minutes of starting their lunch meal. All of the patients were taken to Al-Jubail governmental and private hospitals and most of them needed admission. We started an investigation to identify the food item responsible for the outbreak and determine the source of this food poisoning.
Methodology
We conducted a case control study. A case (patient) was defined as anyone who ate from the same lunch meal at the same restaurant on 1 June and developed one or more of the following symptoms: vomiting, nausea, or dizziness. The controls were those who ate from the same meal at the same time and place and who did not develop any symptoms. We took a sample of 108 cases and 108 controls and asked them about the item of food they had eaten or drank during the meal, what symptoms they developed, and what had been done for them.
Results
A total of 162 workers developed one or more symptoms, out of them 108 were interviewed; 33 of them were of Filipino nationality, 73 were of nationalities from Indian sub-continent countries (45 Indian, 25 Pakistani, and 3 Nepali), and 2 cases of other nationalities. Most of the patients developed vomiting (95.4 %), and dizziness (53.3%). The mean incubation period was 16 minutes and the epidemic curve suggested a common point source outbreak. Special meals were prepared for Filipino workers, and other special meals were prepared for other workers. All workers had drunk the same juice which was prepared at the place of work. Juice was the most significant food item associated with this outbreak (OR = 24.26; Confidence Interval CI =11.67 - 50.45). All samples (food, stool, vomitus, and blood) were negative for common known organisms and chemical agents that regional lab was able to test for.
Conclusion
No laboratory findings were suggestive of any biological or chemical cause for this outbreak. However, the possibility of chemical poisoning remains, because of the short incubation period, short duration of illness, and the nature of industrial environment where the juice was prepared.