Case cluster found in Salmonella outbreak

Jun 16, 2008 (CIDRAP News) –The US Food and Drug Administration (FDA) said that a localized cluster of nine cases has emerged in the nationwide Salmonella outbreak linked to tomatoes, giving officials a solid lead in their hunt for the source of contaminated produce that has so far sickened 277 people in 28 states.

In a conference call with news reporters today, David Acheson, the FDA's associate commissioner of foods, declined to name the geographic region or where the people consumed the tainted tomatoes. "I'm hopeful that this is our most fruitful lead to date," he said.

The illnesses are linked to an unusual strain, Salmonella enterica serotype Saintpaul. In early June the Food and Drug Administration (FDA) warned consumers not to eat raw red plum, red Roma, or red round tomatoes, or products that contain any of those varieties, unless the growing areas are on a list posted on the agency's Web site.

Based on interviews with 202 people, illness onset dates ranged from Apr 10 to Jun 5. At least 43 people were hospitalized, according to an update today from the CDC. Though no deaths have officially been linked to the outbreak, a Texas man in his sixties who died of cancer was infected with the outbreak strain, which may have contributed to his death, the CDC has said.

Acheson said the identification of the case cluster is helpful because it allows investigators to better trace the source of the tomatoes, from foodservice facilities to distributors and possibly to the farm. "The weakest link is individual patient recall," he said. "But with a cluster you have invoices and other records to look at."

FDA officials said they were prohibited from naming the region and where the people who were part of the cluster may have eaten. However, Tim Hadac, a spokesman with the Chicago Department of Public Health, said nine people got sick with Salmonella infections after eating at a Chicago restaurant in mid May, according to a Jun 13 Bloomberg News report. Hadac told Bloomberg that the restaurant has multiple locations around Chicago but isn't part of a national chain. It's unclear if the cluster the FDA identified is the same as the Chicago one.

Ian Williams, chief of the Centers for Disease Control and Prevention's (CDC's) OutbreakNet team, told reporters that the agency still considers the outbreak ongoing.

Officials said they have not ruled out tomatoes from southern Florida and Mexico as the possible source of the contaminated tomatoes. Both were harvesting tomatoes and were major suppliers to the US market in early April when the S Saintpaul infections started occurring.

However, the FDA has cleared tomatoes from northern Florida growing regions because they are just now being harvested and weren't available at the start of the outbreak. Acheson said some retailers are selling those tomatoes and are posting certificates from the state of Florida verifying that they are from northern Florida. He said growing regions in central and southern Florida are no longer harvesting tomatoes.

Florida intensified its tomato testing program after the outbreak was announced, Acheson said. Though all samples so far have been negative, testing did not begin until after the central and southern Florida tomato harvests had ended, he said.

The FDA has stepped up sampling on tomatoes entering the United States from all regions of Mexico, Atcheson said, but he added that the FDA doesn't have the authority to stop shipments without evidence that tomatoes from a certain growing region are the source of the outbreak. If the contaminated tomatoes are from Mexico, he said, there is a chance that the products are still entering the United States.

Tomatoes from the Baja region of Mexico, however, have been cleared, because the area did not begin harvesting tomatoes until after infections began, FDA officials said.

Federal food safety officials are communicating with their counterparts in Mexico to determine if any Mexicans have had illnesses that match the outbreak strain, he said.

See also:

Jun 16 CDC press release

Jun 13 CIDRAP News story "Congress voices frustration as Salmonella toll rises"

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