[Study of 2 food poisoning outbreaks in Mora (Toledo) with the same source of infection]

The occurrence of an outbreak needs an immediate investigation, because on it depends the necessary measures to control the spread of the epidemic, and it is also the way of knowing the causal factor. We present the results of the investigation of two food poisoning outbreaks (outbreak A and outbreak B) occurred in Mora (Toledo). Both outbreaks were reported at the same time, the source of infection was the same and the total number of exposed people was 620.

A case-control study was carried out. A standardised questionnaire for food poisoning outbreaks was used to collect the data. Data were analysed using classic methods and also logistic regression models.

A total of 236 individuals were interviewed (119 for outbreak A and 117 for outbreak B), 146 of them were cases (73 in each outbreak). The mean incubation period was of 26.18 (+/- 12.35) and 25.2 (+/- 19.9) hours respectively. The main symptoms were diarrhoea, fever and abdominal pain. The mean age of the cases was 43.42 (+/- 17.03) years old for outbreak A and 42.4 (+/- 19.9) for outbreak B. The statistical analysis showed a significant association between the intake of cake and the disease (adjusted odds ratio = 25.00; 95% confidence interval = 6,4996.15 for outbreak A and adjusted odds ratio = 64.62; 95% confidence interval = 8.10-515.3 for outbreak B). We also obtained a laboratory confirmation showing the presence of Salmonella Entérica I, Infantis 6.7:r:1.5 in samples of cases, cake and samples of the person who prepared the cake.

The logistic regression model, used for the analysis was useful to detect and summarise data in a more efficient manner than simple stratified analysis. The collaboration of the Primary Health Care professionals contributed to the success of the investigation.