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.