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Salmonella outbreak among attendees of two wedding parties, Riyadh, Saudi Arabia, July 2000.


On July 1st 2000, an outbreak of food poisoning occurred among attendees of two wedding parties at two "esterahas" south of Riyadh. The objectives of this study were to identify the cause(s) of this outbreak, to assess its extent, and to suggest recommendations for preventing occurrence of similar outbreaks in the future.


We attempted to interview all individuals who had attended either party and had eaten from the party foods, whether they had developed any symptoms of food poisoning or not. A list of food items served at both parties and their preparation techniques was collected.


Among attendees of party A, 205 had eaten party food, 134 of who became sick (Attack rate [AR] = 65.4 %). Of those sick participants, 113 (84.3 %) sought medical care and 15 (11.2 %) of them were hospitalized. Among attendees of party B, 36 had eaten party food, 26 of who became sick (AR = 72.2%), 20 (76.9%) of them had consulted a physician and only one (3.8 %) was hospitalized. Attendees of both parties had eaten the same food items at nearly the same time interval. The median incubation period for illness in both parties was 15 hours. Of all eight-food items served at both parties, mayonnaise salad was the only food item in common that was associated with the outbreak at both parties. Mayonnaise salad was prepared by an asymptomatic food-handler, after which it was kept for a median of five hours at room temperature before serving. Salmonella group B non-typhi was isolated from 48 patients, whereas salmonella of an unidentified serogroup was isolated from 10 patients. Two food-handlers had a positive rectal swab for salmonella group B.


Salad mayonnaise was the most likely vehicle of this outbreak. The potatoes added to the salad were probably contaminated during preparation by the asymptomatic food-handler, who is thought to be the source of the outbreak. Time-temperature abuse was the principal factor in producing this outbreak. Other food items associated with this outbreak at party A were most probably cross-contaminated during serving. Promotion of health education to food handlers was recommended, along with application of hazard analysis critical control point to routine inspection of restaurants. Salmonella-excreting food-handlers should not be allowed to handle food until their stool culture proves negative for at least 3 times.