U.S. tomato-linked salmonella illnesses surpass 800

A pile of tomatoes are seen on display at a wholesale produce market in Washington, June 12, 2008.

WASHINGTON (Reuters) - The number of people sickened in a salmonella outbreak linked to certain tomatoes has topped 800 as U.S. investigators continue to try to pinpoint the source of the contamination.

The U.S. Centers for Disease Control and Prevention said on Friday at least 810 people in 36 states and the District of Columbia have gotten sick after eating tomatoes.

CDC officials said this is the largest salmonella outbreak connected to produce.

Investigators and scientists looking at possible points of contamination along distribution and packing chains have tested approximately 1,700 samples, primarily tomatoes, and all of them have come back negative, Dr. David Acheson, associate commissioner for foods at the Food and Drug Administration, told reporters.

"It isn't over yet and we don't have all the answers," he said.

Investigators will continue to collect water and other environmental samples for testing and conduct tests in food-handling facilities.

One trend that officials have come across during their investigation, Acheson said, is a high rate of repackaging in the industry.

Acheson said the FDA has heard from professionals in the industry that as many as 90 percent of tomatoes may be repacked. This is due often to consumer requests for certain sizes of tomatoes. Suppliers or distributors will many times go through different boxes of tomatoes and repackage them together to fit customer requests, Acheson said.

Dr. Patricia Griffin of the CDC said although officials "continue to see a strong epidemiological association" between consuming certain types of identified tomatoes, health officials are not completely ruling out other possible sources of the outbreak.

"We always keep an open mind about the possible cause of an outbreak," she said.

Griffin noted that outbreaks connected to produce are hard to track because people often eat many different types of produce together.

No deaths have been blamed on the outbreak. However, one elderly man in Texas who died of cancer was infected at the time of his death. Officials said the infection may have played a role in his death.

Federal officials continue to work with state and local investigators, especially in places like Texas where large clusters of illnesses have been found.

The FDA and CDC are also looking at their own system for tracing the outbreaks, Acheson said. Any changes to this process would have to be part of a joint effort by regulators and lawmakers, he said.

"The (system) we are operating under currently clearly isn't getting us an answer fast enough," Acheson said.

Health officials have linked the outbreak to raw plum, Roma and round tomatoes. Salmonella Saintpaul, the strain involved in the outbreak, is rare, CDC officials said. Typically, the CDC sees only about 400 cases of Saintpaul infections in humans each year.

Salmonella can cause fever, diarrhea, nausea, vomiting and abdominal pain, according to the FDA.

A list of tomato-growing states that have been cleared by health officials is posted on the FDA website here#outbreak.

(Reporting by Georgina Coolidge; editing by Jim Marshall)