Salmonella in Del-Monte cantaloupes: epidemiology is faster, more powerful than laboratory confirmation

Posted: September 27th, 2011 - 10:06am by Doug Powell

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As part of continuing coverage of the yes-it-was-salmonella-in-Del-Monte-cantalopues-that-made-people-sick-no-it-wasn’t lawsuit, Kirk Smith, epidemiology supervisor for the Minnesota Department of Health, told the Washington Post it’s rare for scientists investigating foodborne illness outbreaks to test the exact food suspected of carrying pathogens. By the time symptoms occur and a foodborne illness is reported and confirmed, the product in question has likely been consumed or has exceeded its shelf-life and been thrown away.

Instead, scientists, like detectives, interview victims, collect data, analyze patterns and match food “fingerprints” to determine the likely source of an outbreak.

“The majority of outbreaks, we don’t have the food to test,” Smith said. “Laboratory confirmation of the food should never be a requisite to implicating a food item as the vehicle of an outbreak. Epidemiology is actually a much faster and more powerful tool than is laboratory confirmation.”

The Post also uncovered some e-mail exchanges between Oregon state epidemiologist William E. Keene and Del Monte execs.

Keene wrote in an e-mail to the company on March 19 that evidence the company’s cantaloupe was the source of contamination was “overwhelming. … I think we need to move ahead with the common understanding that your cantaloupes caused this outbreak.”

Keene included in the e-mail an epidemiological analysis of cantaloupe consumption in the United States and how it relates to the U.S. share of cantaloupe from a farm in Guatemala that supplies Del Monte Fresh Produce. He used this analysis to explain the high probability that the contaminated cantaloupe originated from the farm, located in AsuncionMita.

“In our world, these numbers are considered pretty good evidence, however circumstantial,” he wrote.

Thomas Young, Del Monte Fresh Produce’s vice president of research and agricultural services, wrote in one e-mail, “I cannot imagine how [salmonella] could be coming from our Mita operation, but I am available to assist you in your investigation.”

Young also argues that none of Del Monte Fresh Produce cantaloupes tested positive for Salmonella Panama. Keene responded that a positive test “is a pretty tough standard to meet,” given the fact that the implicated cantaloupe had already been consumed and whatever remained had likely been thrown away.

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