On 18 October 2019, several cases with gastrointestinal symptoms of abdominal pain and diarrhea, were reported among labourers living at Mortco Executive Compound in Jubail city, Saudi Arabia. The symptoms appeared on the same day after consuming a meal served at the compound's kitchen. A team from the Saudi Field Epidemiology Training Program was dispatched to investigate the outbreak, find out its source and to implement control measures.
Methodology
The investigative team visited the compound and interviewed patients and food handlers. A retrospective cohort study was conducted. A case was defined as any person suffering from symptoms of foodborne illness (e.g. diarrhoea and/or abdominal cramps) after eating from the plated meal menu served at the compound on 18 October, 2019. We calculated relative risk and attack rates for each food item. We inspected the kitchen and food preparation areas, and information was obtained on food preparation practices. Food and water samples were obtained, along with stool specimens from symptomatic cases and anal swabs from food handlers. Data was analysed using Microsoft Excel 2016 and SPSS.
Results
We identified 53 cases with an overall attack rate of 49% (53/109). Of those, 39 (74%) had sought medical advice with no reported hospital admission or deaths. Symptoms started at 9:00 p.m. on the same day of consuming a meal served at the compound's kitchen between 12:00 to 01:00 p.m. Cases ranged in age between 20-56 years (mean=33 SD±7). The most commonly reported symptoms were diarrhea (100%) and abdominal pain (90%). The peak incubation period was 9 hours. Illness was significantly associated with consumption of oriental chicken soup (RR=18.26, CI=6.06-55.04, p<0.0001). Stool analysis and culture were negative for both cases and food handlers. Food and water samples sent for microbial analysis were also negative.
Conclusion
Our investigation identified oriental chicken soup served during lunch as the most likely source of the outbreak, although the specific organism was not identified. Clinical and epidemiological evidence suggests Staphylococcus aureus or Clostridium perfringens as the source of infection. Rapid detection of foodborne pathogens and toxins are critical to accurately identify the sources of outbreaks so that precise control measures can be implemented.