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An Outbreak of Salmonellosis in an extended Family in Riyadh, 19-20 Shaaban 1415 H (20-21 January, 1995)


On 20th of Shaaban 1415 H (21 January 1995) the Malaz Selective Primary Health Care Center (SPHCC) was notified by Alsalam PHCC that 14 members of one family reported symptoms of diarrhea, fever, vomiting and abdominal cramps. Initial investigations revealed that four related families had gathered at their grandfather's house on Friday 19th of Shaaban (January 20th). At 9 p.m. they brought dinner from a restaurant. Six hours later they developed symptoms of gastroenteritis. We began an investigation on 22nd of Shaaban (January 23rd) to determine the extent of the outbreak and the risk factors for illness.


A case was defined as any person among the four families who visited the grandfather's house during 17-19 Shaaban and reported having three or more diarrheal stools in a 24-hour period with fever, abdominal cramps and vomiting, and stool culture positive for salmonella. Both private and governmental PHCCs were asked about any patients with symptoms of gastroenteritis or fever admitted or treated during January 20-23rd. A retrospective cohort investigation was conducted among the four families (21 persons). We interviewed patients and food history was obtained for the three days preceding the onset of illness. Rectal swabs were collected from the patients and from the workers in the restaurant.


We identified 14 cases among the total of 2l persons in the four families. Seventeen had eaten the dinner on 19th of Shabban (Jan. 20); 14 (82%) became ill and 3 (18%) remained well. The median incubation period was 13 hours and the median duration of illness was 10 hours. No one was hospitalized; and 100% reported having fever (median temperature = 38.8°C), diarrhea (l00%), abdominal cramps (l00%), and vomiting and nausea (60%). There were 13 (62%) females and 8 (38%) males. The median age of cases was 23 years. 10 rectal swabs from cases were positive for Salmonella. None of the restaurant staff were sick but one rectal swab was positive for Salmonella. The only meal shared by all four families was the Friday meal. There was no association with eating any food items at Friday lunch with illness. All 14 patients had eaten chicken shawarma at Friday dinner. Eating chicken shawarma is the single most likely risk factor for illness. The attack rate (AR) among persons exposed (eating shawarma) was 82%, and the AR among those not exposed (not eating shawarma) was 0 (RR INF; p0.005, Fisher's exact test). 95% undefined.


This is a common source outbreak which occurred after eating dinner from a public restaurant. The chicken shawarma was the most probable vehicle of transmission. Cross-contamination as well as inadequate internal temperature of the cooked chicken were most likely responsible for this outbreak. Education and training of food handlers in proper food handling practices should minimize this problem.