(HealthDay News) -- Experts at the U.S. Centers for Disease Control and Prevention now say they're no longer sure that the nationwide salmonella outbreak is due to tomatoes alone, or some other food source.
"Whatever this produce item is that's causing illness is probably still out there making people sick," Dr. Patricia Griffin, chief of the Enteric Diseases Epidemiology Branch at the CDC, told reporters late Friday at a special press teleconference. She did not say what source other than tomatoes, if any, might be suspected.
The number of people sickened in the outbreak has now jumped to 810 across 36 states, according to the latest CDC numbers presented Friday.
Health officials said the most recent reported case of infection with Salmonella Saintpaul occurred June 15. However, more illnesses may be waiting to be identified: According to experts, it typically takes an average of 16 days before doctors can pinpoint the onset of an infection.
The exact source of the outbreak remains unknown. Tomatoes are still considered the most probable cause, stressed Dr. David Acheson, the U.S. Food and Drug Administration's associate commissioner for food protection.
"The most recent case appeared to have onset just 12 days ago, and that raises the question is there something still out there that people are consuming that is leading to illness," he said. "Just because the outbreak is ongoing doesn't mean it can't be the tomatoes. It certainly could be the tomatoes, there's nothing to indicate that we should be looking at anything else," he said.
"We have no evidence that the outbreak is over... I would say that the source of contamination has been ongoing at least through early June and we don't have any evidence that whatever the source is has been removed from the market," Griffin said.
One factor complicating the search for the cause of the outbreak is a common industry practice called "repacking."
"Repacking is a situation in which a supplier or a distributor will repack tomatoes to meet a specific customer's request," Acheson explained. "So, if a customer is wanting small, ripe tomatoes and the supplier does not have a box of small ripe tomatoes, then they will typically go through multiple boxes and pull out ones that meet customers' specifications and repack them. It's a very, very common practice. We've seen reports that it may be as common as 90 percent of tomatoes get repacked, but we don't have confirmation that the number is that high. Obviously this complicates the trace-back," Acheson said.
He also said that it was possible that tomatoes were contaminated at a packing and distribution center, not a particular farm. That means that produce from states that have been cleared may have gone through packing or distribution houses elsewhere, and become contaminated there.
The food poisoning scare ranks as the largest on record in terms of illnesses linked to tainted produce, the CDC said. "This is so far the biggest outbreak with this number of illnesses confirmed by culture," Griffin noted.
More than 300 of the total cases from the current outbreak come from Texas. Patient ages range from under 1 year old to 99 years old. Half the victims are women.
In addition, at least 95 people have been hospitalized; there have been no deaths, the CDC reported.
The FDA had sent teams of investigators to Florida and Mexico as of last weekend to inspect farms, packing houses and distribution centers. There has been no word yet on what has been found.
The increase in people sickened by salmonella was not unexpected. Three weeks ago, the count was below 200; it jumped to more than 380 a week later.
The CDC had predicted last week that for every reported case, there would be 30 more that had gone unreported.
And health officials had warned that the end was not yet in sight.
"The marked increase is not due to new infections, but mainly because some states improved surveillance in response to this outbreak, and laboratory identification of many other previously submitted strains has now been completed," said Casey Barton Behravesh, an epidemiologist with the U.S. Centers for Disease Control and Prevention, during a June 19 teleconference.
According to the numbers on the CDC's Web site -- which do not include the latest cases -- the victim count breaks down by state to: Arkansas (10 persons), Arizona (38), California (10), Colorado (6), Connecticut (4), Florida (1), Georgia (15), Idaho (3), Illinois (66), Indiana (11), Kansas (11), Kentucky (1), Maryland (25), Massachusetts (17), Michigan (4), Missouri (12), New Hampshire (3), Nevada (4), New Jersey (4), New Mexico (80), New York (18), North Carolina (5), Ohio (3), Oklahoma (17), Oregon (7), Pennsylvania (6), Rhode Island (3), Tennessee (6), Texas (330), Utah (2), Virginia (22), Vermont (1), Washington (4), Wisconsin (6), and the District of Columbia (1).
On June 20, Acheson said the investigation into the outbreak had zeroed in on "a number of farms" in both Florida and Mexico.
Health officials have said all along that the bulk of the tomatoes available at the start of the outbreak in mid-April had come from Mexico and parts of Florida.
Salmonella is a bacteria that can cause bloody diarrhea in humans. Some 40,000 cases of salmonellosis are reported in the United States each year, although the CDC estimates that because milder cases are not diagnosed or reported, the actual number of infections may be 30 or more times greater. Approximately 600 people die each year after being infected.
However, the strain of Salmonella Saintpaul had been previously considered rare. In 2007, according to the CDC, there were only three people infected in the country during April through June.
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By Sean Kelley
