PulseNet Surveillance System Used by CDC Reduces Costs, Saves Lives
Founded by the CDC in 1996, PulseNet is a self-described “national network of laboratories that solves outbreaks of foodborne disease,” that rapidly identifies “outbreaks – large and small – by connecting the dots between cases of similar illness that are happening anywhere in the country.” The network is composed of 87 local, state, regional and federal public health and food regulatory agency laboratories – at least one in each state – that test foodborne disease bacteria using pulsed-field gel electrophoresis (PFGE) and a newer method, whole genome sequencing (WGS), to detect and record the DNA fingerprint of the pathogen. During an outbreak investigation, scientists can use PulseNet to identify the type of bacteria that caused people to get sick, determine the cause of the outbreak, and find out what happened to contaminate the source food.
The Outbreak Behind PulseNet
In 1993, an outbreak of E. coli in the western United States was linked to 732 illnesses and the death of four children. It took over one month after the first outbreak case for investigators to identify E. coli as the cause of the illnesses. It took investigators another two weeks to identify hamburger patties as the source of the outbreak – a full six weeks after the first person fell ill.
After the outbreak, scientists at the CDC decided that outbreaks could be stopped sooner if all public health laboratories could perform the same DNA fingerprinting tests on bacteria from patients and share the results of thos tests with other laboratories across the nation. The CDC worked with the Association of Public Health Laboratories to develop the system, officially launched in 1996, with the goal of obtaining DNA fingerprints of all foodborne bacteria as they were submitted to state public health laboratories, gather the information locally and nationally, and continuously monitor the database for clusters of cases with the same DNA fingerprints.
Internal Workings of a Foodborne Surveillance System
The team of CDC PulseNet scientists compares DNA fingerprints submitted from across the country. They look for clusters – groups of matching patterns – that are increasing more now than in the past. The PulseNet team can trigger an investigation by rapidly identifying increases in reported illnesses from across the US.
CDC scientists then investigate the illness clusters identified by PulseNet. The cluster is classified as an outbreak if they find links between cases. Laboratories that submitted the patterns receive reports of the results. Results are also posted to the PulseNet message board.
Approximately 1,500 clusters of disease are identified by state and local health agencies annually, and around 30 multistate or national outbreaks are identified.
PulseNet Saves Lives, Money
More than 270,000 illnesses are avoided annually as a result of PulseNet analysis and surveillance. In addition to the 270,000 lives saved by surveillance efforts, even more illnesses are prevented because of industry improvements and better-informed government and consumers. The illnesses avoided by improvements in industry and knowledge cannot be quantified and were not included in the study results, but illnesses from foodborne pathogens “likely were” decreased by these factors, said Robert Scharff of Ohio State University.
The savings in medical costs by preventing illnesses break down as follows: $478 million saved by prevented Salmonella infections, $20.4 million by prevented E. coli infections, and $8.7 from prevented listeria infections.
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