On June 21st 2001, several patients presented to ER of Prince Salman Hospital, Riyadh, Saudi Arabia with gastroenteritis symptoms. They all gave history of have eating shawarma from a restaurant at Oraija, Western Riyadh, the previous night. The objective of this study was to identify the source of the outbreak, to assess its extent and to suggest recommendations to prevent occurrence of similar outbreaks in the future.
Methodology
A case definition was developed. A case was defined as any individual who had developed diarrhea (more than three loose motions per 24 hours) with any of the following symptoms: abdominal pain, fever or vomiting within three days of eating at restaurant A on 20th June 2001. Hospitals and health centers in South-West of Riyadh were searched for cases. Patients and un-effected family members were interviewed about food eating from the restaurant. Food specific attack rates and risk ratio for each food item was calculated. We reviewed the usual routine preparation, source, handling and storage of food.
Results
A total of 147 individuals were interviewed. 68 (46.3%) of them developed gastro-enteritis, most commonly manifested by diarrhea (100%), fever (86.8%), abdominal pain (83.8%) Majority of interviewed persons were Saudis 139 (94.5%). Of 68 total cases, thirty-three (48.5%) were males, and 35 (51.5%) where females, yielding a 1: 0.9 male to female ratio. The mean age of cases (+ SD) was 18.3 (+ 13), with a range of 1 - 75 year. The median incubation period was 8 hours and the epidemic curve suggested a common point source outbreak. Among food and drink items consumed on Wednesday June 21, chicken shawarma showed the highest risk ratio (the highest significant association with Gastroenteritis) RR = 15.9 (95% CI of 6.8 - 37.2). The attack rate for eating shawarma sandwiches was (96.6%) compared to (6.1%) among those who did not. Out of 44 stool samples collected from cases, 42 (95%) grew (Salmonella group D non-typhi).
Conclusion
Shawarma sandwiches served by restaurant A, western Riyadh, caused this foodborne Salmonella outbreak. Chicken was the most likely source of infection. Time temperature abuse as well as inadequate heat treatment were the most important factors leading to this outbreak. Nation wide health education and training programs that emphasize the importance of proper food handling practices, personal hygiene, and food sanitation can be of value as preventive measures. Food handlers, in particular, should be targeted. Proper food delivery by well-equipped trucks is strongly recommended.