PulseNet Computer Network
Powers Outbreak Detection

The CDC's PulseNet national information-sharing computer system tracks foodborne disease, which relies on information from states.

By Dustin Volz

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Nearly two decades ago, epidemiologists weren’t aware of an E. coli outbreak in the Pacific Northwest until 39 days after the first person fell ill.

Public health officials began an investigation only after a physician at a Washington children’s hospital noticed an increase in the number of patients showing symptoms associated with E. coli.

The U.S. Centers for Disease Control and Prevention and state health departments traced the outbreak to hamburgers sold at the fast-food chain Jack in the Box – but not before it killed four children and sickened 700 people.

“It took a very long time for the public health system to recognize the outbreak,” said Dr. Bala Swaminathan, then a senior adviser for laboratory science at CDC.

Following the outbreak, Swaminathan led a team of scientists who devised a system intended to reduce the lag time. The result: PulseNet, an information-sharing computer database that allows labs across the country to quickly upload and compare vital microbiological data essential to outbreak detection.

While it took a month or longer to identify an outbreak 20 years ago, PulseNet has slashed that time in half to 15 to 18 days, Swaminathan said.

Launched in 1996, PulseNet matches results from a DNA-identifying technique called pulse field gel electrophoresis. Lab technicians use it to “fingerprint” bacteria and discern whether cases of foodborne illness are from a common source.

The DNA test was developed in the 1980s, but before PulseNet it was not effective in helping labs share and match fingerprint patterns, Swaminathan said. Because of variations in labs and personnel and insufficient technology, results submitted to CDC from health departments in every state frequently left scientists unable to match cases of foodborne illness, he said.

“About 70 percent of the outbreaks we start investigations for are initiated through PulseNet,” said Ian Williams, chief of CDC’s outbreak response and prevention branch. The rest begin when state health departments notice something unusual, he said.

PulseNet costs less than $10 million per year to operate annually and saves nearly $300 million a year in costs associated with foodborne illness, according to a 2010 study by Dr. Robert Scharff, an economics professor at Ohio State University.

PulseNet’s success – as well as an increasingly global food trade – has led to PulseNet International, which coordinates data-sharing worldwide. Networks now serve Canada, Asia Pacific, Europe, Latin America, the Middle East and Africa.

PulseNet has dramatically improved how epidemiologists solve foodborne disease outbreaks, but a reliance on state funding affects the network’s effectiveness, Swaminathan said, adding that “states have not achieved their full potential.”

More funding would let them to process and report more tests, which would allow outbreaks to be identified more often and sooner, he said.

Resource limitations are a reality for every state, Williams said, and each functions independently, meaning CDC relies on them to be diligent in testing and reporting cases.

“One of the challenges across the United States is every state does things differently,” Williams said. “An important thing to remember is the states don’t work for CDC.”

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