Food Poisoning amongst Census Enumerators, Gokwe South, Zimbabwe, August 2012

Abstract

Background: Zimbabwe implemented a national census from the 18 to the 28 August 2012. On 15 August 2012, a report was received of gastrointestinal illness among census enumerators during training in Gokwe. A total of 729 enumerators and 180 supervisors attended this training. More than 300 enumerators fell ill. We investigated the outbreak to characterize the illness and identify the causative agent. Methods: We conducted a retrospective cohort study. We used snowballing to identify and recruit respondents. We interviewed 117 enumerators to collect data on signs and symptoms of illness and food items consumed. Food preparation surface and rectal swabs for culture were collected. Data was analyzed using Epi Info™ to generate frequencies, means, proportions, relative risks (RR), and attributable risks (AR), and 95% Confidence Intervals. Results: We interviewed 117 enumerators. Median incubation period was 7 hours (Q1=6; Q3=11). Different kitchens were used for preparing supervisors’ and enumerators dishes but source of food was the same. Common signs and symptoms included abdominal cramps – 71%, watery diarrhoea – 67%, nausea – 52%, and fever – 27%. All patients fell ill within one incubation period. Eating beef during lunch on 14/08/12 was associated with illness (RR=5.07, 95% CI=2.05 – 12.57). The AR for beef was 63%. Leftover food was unavailable for laboratory analysis. Staphylococcus aureus was isolated from patients, food handlers and serving table surface. Conclusions: This was a food poisoning outbreak, likely due to S.aureus pre-formed toxin. Beef consumed during lunch on 14/08/12 was the possible source of infection. Contamination could have occurred during food storage. Storage temperatures of food prepared for mass gathering should be monitored. Involvement of health department in planning and food handlers training recommended.