Foodborne Salmonella Outbreak in Sulyyel, 2002

On October 3rd 2002, many patients with gastroenteritis symptoms presented to Sulyyel hospital, after attending a wedding party. On October 7th, the Field Epidemiology Training Program team was requested to investigate this outbreak. The objectives of this study were to identify the source of the outbreak, to assess its extent and to suggest recommendations for preventing occurrence of similar outbreaks in the future.

The investigating team met with the hospital director and the involved doctors, nurses, health inspectors and sonic of the party attendees. The emergency room records were reviewed, and admitted patients were interviewed. A preliminary list of patient's names, addresses, telephone numbers and name of treating health facility was obtained and the active surveillance done by the hospital was revived. A cohort study was conducted. A case definition was develope41 which included any individual who developed diarrhea with or without ,abdominal pain, vomiting and fever within 3 days of eating at the wedding ceremony in Sulyyel city.

To recruit the cohort, initially the groom was requested to provide the list of guests, who had attended the wedging party. As the groom was not cooperative, other patients and attendees were traced through the known patients, their relatives and local notables. Two field work teams were organized composed of one doctor, one health inspector, two female nurses and a driver, each. The attendees were interviewed, face to face, using a structured questionnaire that inquired about demographic data, symptoms of gastroenteritis, date and time of eating dinner, date and time of onset of symptoms, food items eaten, history of hospitalization and any recent 'history of diarrheal illness. Information on hospital course were obtained from Sulyyel hospital and other health facilities.

Regarding the restaurant food handlers, an open-ended interview was conducted inquiring on the food items prepared, ingredients, preparation techniques, methods of preservation, job description of each food handler and availability of health certificates. They were examined for their level of hygiene, external injuries and skin infections. The restaurant was visited and inspected for general sanitation; including the cleanliness of the food preparation site, food storage area and utensils. Swabs had been already taken randomly from different sites including tables, utensils and refrigerators, by municipality staff. Stool cultures were done for all diarrhea patients, while rectal swabs were taken from the food handlers.

The wedding ceremony was held in an open yard surrounded by houses in the eastern part area of Sulyyel city. The food consisting of rice, meat, salads and sweets was served in two shifts, first at 10 p.m. and then at 2 a.m. Out of approximately 300 persons who had attended the wedding party, a total of 238 were traced and interviewed. Their ages ranged from 2 to 80 years (mean 23.5). Of the interviewed guests 89.1% were Saudis and 47.1% were males. All had eaten at the wedding, 50.4% at 10:00 p.m. (10% were females) and 49.6% at 2:00 a.m. (96.6% were females).

Out of all those interviewed 88 (37%) fulfilled the criteria of case definition. All patients developed diarrhea, other common symptoms were colicky abdominal pain (94.3%), fever (86.4%), vomiting (64.8%), headache (48.9%) and nausea (30.7%). Colicky abdominal pain was the first symptom that appeared in 43.2% of patients, followed by fever in 35.2%, and then diarrhea in 11%.

Patients started experiencing symptoms at 1:00 a m. on October the 3rd 2002. The incubation period ranged from 3-78 hours (mean=20.6, median=21). The epidemic curve suggested a common point source outbreak. Out of all patients, 88.6% sought medical care, all at Sulyyel hospital. Of those who sought medical care 70.5% were hospitalized. All patients recovered with no complication.

Out of 9 food items and drinks served in the wedding ceremony (Table 1), 3 were significantly associated with illness; meat ranked first (RR=16.7, 95% CI=2.37-115.8), followed by rice (RR=1.95, 95% CI=1.95-93.61) and restaurant made sweets (RR=1.2, 95% CI=1.35-2.58). It was also observed that risk of disease significantly increased with eating at 2:00 a.m. as compared to 10:00 p.m. (RR 2.18, 95% CI= 1.51-3.15), and use of food remnants (RR 4.81, 95% CI 3.54-6.53). The attack rates and risks associated with eating meat and rice increased with eating late or consumption of food remnants.

It was observed that the quality of hygiene at the restaurant was poor. All 9 restaurant workers denied a recent or past history of diarrhea; while none possessed a valid health certificate. Food preparation at the restaurant started at 2 p.m. on that day and was-ready by 7 pm. At 9 p.m. the food was transported to the wedding site, and served without reheating at 10 p.m. and 2 a.m. In the second shift, unheated remnants of the earlier food were also served.

Salmonella group C non-typhoid was isolated from 40 (45.4%) patients and one patient had both Salmonella group B and C. All restaurant workers had salmonella group C. The swabs taken from the restaurant were positive for coliforms. No food samples from the food remnants was available by the time the investigation started.

This is a typical example of a food poisoning outbreak associated with poor food hygiene and time-temperature abuse. The incidence of salmonellosis is reported to have increased worldwide in recent years.[1] In a review, it was found that Salmonella spp. was the causative organism in 33% of food poisoning outbreaks in the Eastern province during the period 1991-1996.[2] In the year 2002, 2539 cases were reported from all-over the Kingdom of Saudi Arabia with a rate of 211.6 cases per month.[3]

Presence of the Salmonella, either in the slaughtered animal's body or contamination of the meat by the food handlers at multiple stages of preparation of the food for the wedding ceremony, is not a surprise keeping in view the disease pattern in Saudi Arabia and the known role of food handlers in the transmission of food poisoning.[4]

As obvious from the findings of the study the slow process of cooking, poor food and personal hygienic measures adopted by the restaurant staff, storage of food at luke-warm temperatures, serving the remnants of food in the second shift without reheating was contributory to the large number of cases in this accident_ Involved issues include deeply embedded cultural practices and poor education of food handlers.

It is recommended that a multi-pronged approach should be adapted focusing on improving supervisory mechanism and health education of food handlers and general masses, to prevent occurrence of such incidents in future.