Background.A mean of ≥1000 foodborne disease outbreaks (FBDOs) causing ≥20000 illnesses are reported to the Centers for Disease Control and Prevention (CDC) annually. We evaluated characteristics of successful outbreak investigations (ie, those that identified an etiologic agent or food vehicle) in the Foodborne Diseases Active Surveillance Network (FoodNet).Methods.FBDOs were defined as the occurrence of ≥2 cases of a similar illness resulting from ingestion of a common food. FBDOs reported to CDC Foodborne Disease Outbreak Surveillance System during 2003-2008 with FoodNet supplemental data available were included in the analyses.Results.Data regarding 1200 FBDOs were available. An etiologic agent was confirmed in 715 (60%); a food vehicle was identified in 387 (32%). At least 4 fecal specimens were collected in 425 of 639 outbreaks (67%) with a confirmed etiologic agent and 48 of 232 (21%) without a confirmed etiologic agent (odds ratio [OR], 7.6; 95% confidence interval [CI], 5.3-10.9). A food vehicle was identified in 314 (47%) of 671 outbreaks investigated using a case-control or cohort study, compared with only 73 (14%) of 529 outbreaks investigated by using other methods (OR, 5.5; 95% CI, 4.1-7.3). At least 1 barrier affecting the success of the investigation was reported for 655 outbreaks, including too few patients (n = 172; 26%), too few stool specimens (n = 167; 25%), and too few control subjects (n = 152; 23%).Conclusions.Etiologic agent and vehicle are frequently undetermined in FBDOs. Greater emphasis on fecal specimen collection and overcoming barriers to pursuing analytic epidemiologic studies can improve ascertainment of these factors.
Bibliographical noteFunding Information:
Supplement sponsorship. This article was published as part of a supplement entitled ‘‘Studies From the Foodborne Diseases Active Surveillance Network,’’ sponsored by the Division of Foodborne, Waterborne, and Environmental Diseases of the National Center for Emerging and Zoonotic Infectious Diseases from the Centers for Disease Control and Prevention, and the Association of Public Health Laboratories. Potential conflicts of interest. All authors: No reported conflicts.