Salmonella cases jump as hunt for source narrows

Robert Roos

Jun 20, 2008 (CIDRAP News) Cases identified in a national Salmonella outbreak linked to tomatoes jumped to 552 today as the hunt for the contamination source narrowed to "certain farms" in Florida and Mexico and their distribution chains, US officials announced.

Health investigators have identified 552 people in 32 states and Washington, DC, who were ill with Salmonella enterica serotype Saintpaul, a rare strain, officials announced at a press briefing. That marks an increase of 169 cases and two states over the 383 cases reported 2 days ago.

The bulk of the newly identified cases came from Texas, which now has a total of 265, said Dr. Ian Williams, chief of the OutbreakNet team at the Centers for Disease Control and Prevention (CDC). He said the episode may now be the largest tomato-linked Salmonella outbreak in US history, possibly surpassing one that occurred in 2004.

Echoing statements made Jun 18, Williams said the new cases mainly reflect increased surveillance by state health departments and completion of lab tests, rather than a surge in new cases.

Based on information from 281 patients, illness onset dates ranged from Apr 10 to June 10, Williams said. Fifty-three people were hospitalized, but no deaths have been blamed on the outbreak, Williams said. (As mentioned previously, however, salmonellosis may have contributed to the death of a Texas man who died of cancer.)

Dr. David Acheson, associate commissioner for foods at the Food and Drug Administration (FDA), said an unspecified number of farms in Florida and Mexico are now the focus of the hunt for the contamination source.

"We have completed the trace-backs for some of the tomatoes that have taken us from the point of consumption all the way back to certain farms in Mexico and Florida," he said. He added that contamination could have occurred anywhere along the distribution pathways that connect those farms to consumers, and investigators are "looking all along those pathways to determine where contamination occurred."

"We don't know for certain if the contamination occurred on a farm; it may have occurred . . . in a distribution center, a packing shed, or a warehouse," Acheson said.

He declined to name any farms or say how many are suspected. "We don't have one where we know the problem occurred; we just know they're part of the chain," he said. And the FDA has not yet actually found any tomatoes contaminated with Salmonella, he reported.

Acheson said it's not likely that the contamination occurred in both Florida and Mexico. "It's extremely unlikely that this rare contamination with Salmonella Saintpaul occurred in two places at the same time. . . . It's an unusual serotype, and that would just not make any sense."

He said finding contamination in two places would suggest the possibility of a deliberate act, but he deemed that unlikely. "We've looked into that, and there's no evidence whatsoever that it is deliberate," he said.

The FDA is sending experts to both Florida and Mexico this weekend with the aim of conducting inspections on the farms and throughout the distribution chains, Acheson reported.

He also revealed that Texas health officials have identified a cluster of cases in the state. But he declined to say where or how large the cluster is or if it's linked to any particular retailer or chain of retailers.

"The FDA is working with them [Texas officials] and the CDC to use that cluster as another trace-back in the hope that [it] will further narrow the source of the contaminated tomatoes," Acheson said.

The FDA's message to consumers has not changed, said Faye Feldstein of the FDA's Center for Food Safety and Applied Nutrition. The agency advises consumers not to eat raw red plum, raw red Roma, or raw red round tomatoes unless they come from one of the growing areas that have not been associated with the outbreak, as listed on an FDA Web page (see link below). Cherry and grape tomatoes and tomatoes sold with the vine attached are considered safe.

"The message to consumers is, if you're not sure, don't take a risk," said Acheson.