Health officials continue salmonella probe

(CNN) -- A cluster of nine cases linked to tomatoes from a single source is the "most fruitful lead to date" in an investigation of a 23-state salmonella outbreak, a U.S. health official said Monday.

Dr. David Acheson, assistant commissioner for food protection at the Food and Drug Administration, would not divulge where the cluster was found.

More than 200 people have been sickened since the outbreak was identified.

Isolated reports of illness are more difficult to trace reliably to a single source, he said, because doing so depends on the patient's ability to recall what and where he or she ate several weeks before the onset of symptoms.

Since mid-April, at least 25 people have been hospitalized with Salmonella Saintpaul, an uncommon form of the bacteria. No deaths have officially been attributed to the outbreak, but the infection may have been a factor in the death of a Texas man in his 60s who also had cancer, the Centers for Disease Control and Prevention said.

Cherry tomatoes, grape tomatoes and tomatoes with the vine still attached have been deemed safe, as have tomatoes from northern Florida, Acheson said. Roma plum and red round tomatoes are safe to eat if they are from areas that have been excluded, he said.

A list of such areas is posted on the FDA's Web site.

Cooking would kill the bacteria, but Acheson said consumers were being urged to throw out any suspect tomatoes because that was "the simplest consumer message."

Some stores are posting certificates issued by the state of Florida guaranteeing that their tomatoes were harvested from the northern part of the state, where tomatoes were not yet ripe when the outbreak began, Acheson said.

The harvest of tomatoes from central and southern Florida was halted May 1. Because a tomato's shelf life is four weeks or less, they, too, are unlikely to be the cause of any current sickness, he said.

The state's testing program has turned up no positive results, he said.

The states affected are Arizona (19 persons), California (2), Colorado (1), Connecticut (1), Florida (1), Georgia (7), Idaho (3), Illinois (29), Indiana (7), Kansas (5), Michigan (2), Missouri (2), New Mexico (55), New York (1), Oklahoma (3), Oregon (3), Tennessee (3), Texas (68), Utah (2), Virginia (9), Vermont (1), Washington (1), and Wisconsin (3).

Sampling is also going on in Mexico, said Acheson, who added that he has heard no reports of salmonella illness from that country. The Mexican state of Baja California has been cleared in the outbreak, according to The Associated Press.

The outbreak was identified on April 10 and is considered ongoing, Acheson said.

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