Food poisoning caused by scombroids: A case-control study

The aim of this study is to report the epidemiological characteristics of a food poisoning outbreak due to scombroid fish in a hospital. A case-control study (1:4) was conducted. Patients either symptomatic of food poisoning (cases) or asymptomatic (controls) eating at the hospital cafeteria were included. To identify the source of the outbreak, sanitary control factors were assessed. Microbiological studies and the mast cell tryptase test were performed. All cases and controls received a questionnaire enquiring about symptoms and foods consumed. The odds ratios (OR) for all risk factors and their 95% confidence intervals (CI) were assessed. In total, 20 individuals (90% female) were included in the study: four cases and 16 controls. The overall mean age was 43 years (SD: 10.2). The most frequent symptom observed was facial and neck erythaema (100%). Microbiological cultures were negative, the mast cell tryptase test was normal and breakdown of the cold chain did not occur. The most likely source of the outbreak was fried anchovies (OR: 34.7; 95% CI: 1.50-809.6; p=0.02). Methods suitable to the rapid assessment of the outbreak allowed us to establish prompt preventive measures and identify the likely aetiology.