In 1993 after a large multi-state outbreak of E. coli O157 infections in the Western United States. To prevent future severe outbreaks an effective surveillance network called PulseNet was developed. PulseNet is the national network for molecular sub-typing of foodborne bacteria and is coordinated by CDC. The laboratories participating in PulseNet are in state health departments, some local health departments, USDA, and FDA. PulseNet plays a vital role in surveillance for, and investigation of, foodborne illness outbreaks that were previously difficult to detect. For example, when a clinical laboratory makes a diagnosis of E. coli O157, the bacterial strain is sent to a participating PulseNet laboratory where it is sub-typed, or “DNA fingerprinted” [every E. coli has a unique DNA pattern]. The “fingerprint” is then compared with other patterns in the state and uploaded electronically to the national PulseNet database maintained at CDC, where it can be compared with the patterns in other states. This gives us the capability to rapidly detect a cluster of infections with the same pattern that is occurring in multiple states. The PulseNet database is available to participating laboratories and allows them to rapidly compare patterns. Once a cluster of cases with the same DNA pattern is identified, epidemiologists then interview patients to determine whether cases of illness are linked to the same food source or other exposures they have in common. The strength of this system is its ability to identify patterns even if the affected persons are geographically far apart, which is important given the reality of U.S. food distribution systems. If patients have been exposed to a specific food or to another source of infection, and the case count for that illness is larger than one would expect for the time, the cluster is determined to be an outbreak with a common source.
Another important surveillance network is CDC’s Foodborne Diseases Active Surveillance Network (FoodNet). This network is collaboration among 10 state health departments, the USDA, and FDA. FoodNet conducts active surveillance for foodborne diseases and conducts related epidemiologic studies that look at both sporadic and outbreak foodborne infections to help public health officials better understand the epidemiology of foodborne diseases in the United States and how to target prevention strategies. We have PulseNet to detect possible outbreaks, OutbreakNet to investigate and report them, and FoodNet to track general trends and define where more effective prevention strategies are needed (emphasis added).
These networks stand prepared to detect a public health event related to the food supply. For example, after investigations of PulseNet-identified clusters of E. coli infection focused attention on the need for specific controls during ground beef processing, regulatory and industry practices changed in 2002, and the incidence of E. coli O157:H7 infections began to decrease sharply. By 2005, the incidence of E. coli O157 infections, as measured in FoodNet, had dropped 29%.