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    Source of Largest Salmonella Outbreak in U.S. History May Never Be Found, Says FDA

    June 27, 2008 -- The salmonella outbreak in tomatoes isn't over and it's already the largest salmonella outbreak the CDC has ever tracked, in terms of lab-confirmed reported illness.

    Since the outbreak began in April, the CDC has gotten reports of 810 people in 36 states and Washington, D.C., sickened by Salmonella saintpaul, the outbreak's rare strain of salmonella.

    The most recent onset of illness was June 15, and that may not be the last case, since the CDC gets reports of illness about 16 days after an illness starts, says Patricia Griffin, MD, chief of the CDC's enteric diseases epidemiology branch.

    Griffin notes that in 1985, a salmonella outbreak in milk sickened more than 16,000 people, but those cases weren't all confirmed by lab tests, unlike the number of cases in the current salmonella tomato outbreak.

    Salmonella infection (salmonellosis) can cause diarrhea (which may be bloody), fever, nausea, vomiting, and abdominal pain. Symptoms typically start 12-72 hours after infection.

    Salmonella Tomato Source Unknown

    The FDA hasn't found the source of the tomato salmonella outbreak -- and they admit they may never find it.

    On June 20, the FDA sent investigators to several farms in Florida and Mexico. Those investigators were assigned to probe not only the farms, but the entire distribution chain from plant to plate.

    "It's important to control expectations and it's possible that this investigation may not provide a smoking gun that enables us to pinpoint the source of the contamination," David Acheson, MD, the FDA's associate commissioner for foods, said at a news conference today.

    Part of the problem, Acheson says, is a practice called "repacking," in which suppliers or distributors repack boxes of tomatoes to fit customers' requests. That leads to tomatoes from various sources, domestic and imported, getting mixed together in the repacked boxes, making it hard to trace where the tomatoes have been and where the contamination may have occurred.

    So far, the FDA teams have collected about 1,700 samples for testing -- none of which have shown any signs of Salmonella saintpaul.

    Acheson says it's "not that unusual" for the source of tomato outbreaks to elude investigators.

    "We've dealt with a number in the past and it's not that infrequent for us to be unable to actually trace back specifically to the source," says Acheson. "The whole repacking issue is one of the major reasons why this is so difficult."

    Health officials are also looking at products such as salsa and guacamole that contain raw tomatoes, according to media reports.

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