Outbreaks of food borne diseases in the Lazio region, Italy: the results of epidemiological field investigations.

BACKGROUND

More thorough information about risks, exposures and vehicles of food borne diseases can be obtained from epidemiological field investigations than from infectious disease reports or laboratory data.

METHODS

We analysed the results of 410 field investigations of food borne disease outbreaks reported from 1996 to 2000 and conducted as cohort studies.

RESULTS

The incidence of food borne outbreaks increased from 0.8/100,000 in 1996 to 2.0 in 1999, as did the incidence of salmonellosis (from 16/100,000 to 21 in the same period) and diarrhoea episodes reported by laboratories (from 12/100,000 in 1997 to 29 in 1999). Of the food borne disease outbreaks, 264 (64.4%) occurred in private homes; 5 (1.2%) in hospitals; 31 (7.6%) in canteens and refectories, 84 (20.5%) in restaurants, 41 of which occurred during special functions. The home outbreaks exposed few people (average of 7), had high attack rates (61.7% average) and a high proportion of known aetiology (66%), while food borne disease outbreaks in canteens and restaurants (during special functions) exposed many people (300 and 81, respectively), had medium attack rates (19.7 and 34.5%, respectively) and a higher proportion of confirmed vehicles (50 and 49%, respectively), compared to those occurring at home (21%). Salmonella spp. was the most frequent agent detected in each setting (67% of confirmed cases). The most frequent vehicles at home were mushrooms and sweets containing eggs and cream; in canteens, meat and vegetables and in restaurants, shellfish.

CONCLUSIONS

Outbreak characteristics varied according to the setting. This implies the need for a different approach of field investigations, and different preventive measures.