Nine people sickened by a salmonella outbreak linked to fresh tomatoes ate at two restaurants from the same chain, federal officials confirmed Friday.
The chain's name and restaurant location are confidential, said David Acheson, the associate commissioner for foods at the Food and Drug Administration, during a conference call with reporters. A spokesman for the agency also declined to provide the time frame for the cases -- or say whether the restaurants were in the same state.
The Chicago Department of Public Health identified nine people who ate at a restaurant in May and came down with salmonella, though Tim Hadac, a spokesman for the department, said he did not know whether the nine cases were the same ones Acheson referenced Friday.
None of the nine Chicago victims were hospitalized. Hadac said the department was withholding the name of the restaurant, which he said had several related restaurants in the city but was not part of a national chain.
But FDA officials stressed that the locations where the illnesses were reported were not an indication of where the contaminated tomatoes originated.
"The restaurants are not the problem. The tomatoes are what is making people sick across the country, and we don't know where they came from," spokeswoman Julie Anne Zawisza wrote in an e-mail.
The FDA is tracking several clusters of cases, including the nine chain-based cases, to pinpoint the origin of the rare Salmonella Saintpaul strain, Acheson said.
So far, 228 people have contracted salmonella in 23 states since mid-April, health officials said. Acheson said the "vast majority" of tomatoes produced during the outbreak were "very likely" from Florida or Mexico.
Inspectors are visiting distributors, suppliers and importers in an attempt to track the tomatoes through records, but they have not shown up at any farms because none have been implicated. Acheson said the agency was still trying to ascertain whether the outbreak sprang from a farm or at a packing stage.
Health experts are "still watching to see whether or not the outbreak is ongoing" because they must account for the bacterium's incubation period and the lag in reporting and testing cases, said Dr. Patricia Griffin, chief of the enteric diseases epidemiology branch at the Centers for Disease Control and Prevention.
The probe into the source of the outbreak has been difficult because of the number of victims and the variety of ways they could have contracted the illness, Acheson said. Consumers have avoided tomatoes, prompting farmers to lose millions of dollars as they wait for the fruit to be cleared.
"Doing these trace-backs through these multiple channels are very time-consuming and complex," Acheson said. "We are getting closer, but as of yet, there is no specific geographic location identified."
Meanwhile, Acheson said, the FDA has stepped up its sampling of domestic and imported tomatoes to check for more signs of salmonella.
The FDA is warning consumers to avoid Roma, plum and standard round tomatoes, but the agency has declared cherry and grape tomatoes and tomatoes still attached to the vine to be safe to eat. All California-grown varieties are considered safe because the agency has cleared the state as a source of the outbreak.
"This happens every time," said Seattle attorney and food safety expert William D. Marler. "We've not gotten any better at surveillance of this stuff, though we've got the technology and should be able to figure out outbreaks pretty quick, not a month and a half into it. And not figuring out whether it started from Florida or Mexico -- that's absurd."