Taco Bell Culprit in E. Coli 0157:H7 Outbreak Still Uncertain

ROCKVILLE, Md., Dec. 8 -- Federal investigators said today they are still not sure what's behind the outbreak of Escherichia coli-associated disease at Taco Bell restaurants, even though the chain suspects green onions and has pulled them off its menu.

The investigation is "still very much ongoing," said David Acheson, M.D., chief medical officer for the FDA's Center for Food Safety and Applied Nutrition here.

But the agency has "no data to definitively implicate or rule out any food item," Dr. Acheson said during a press conference.

Taco Bell said Wednesday it would stop serving green onions in its approximately 5,800 U.S. restaurants, after its own testing suggested they were the source for the contamination.

Dr. Acheson said that samples of foodstuffs retained by the restaurant chain and its suppliers are "in our labs and they're being tested." But he said the rapid tests used by Taco Bell to implicate the green onions only deliver a "presumptive positive" that must be replicated using more exact methods.

So far, the outbreak -- which began Nov. 20 -- has caused 63 confirmed cases of infection by E. coli 0157:H7 in six states, according to Christopher Braden, M.D., of the CDC in Atlanta.

Those include 28 in New Jersey, 22 in New York, nine in Pennsylvania, two in Delaware, and one each in South Carolina and Utah. A number of other cases are under investigation, he said, but haven't been definitely linked to Taco Bell.

Dr. Braden said 49 of the patients have been hospitalized, and seven have developed hemolytic uremic syndrome. There have been no reported deaths.

"Illnesses are still occurring and we consider the outbreak to be ongoing," he told reporters.

The outbreak is reminiscent of the recent problem with bagged fresh spinach, Dr. Acheson said, but in that case, investigators were able to pin down the source quickly because more than 80% of the victims said they had recently eaten the vegetable.

In this case, he said, "the common factor is that they all ate at Taco Bell" but it's not clear what foodstuffs all the patients ate.

It's also not yet clear whether the cases in South Carolina and Utah represent separate outbreaks or are part of the cluster centered in New Jersey, Dr. Braden said. Investigators are checking to see whether the patients in those cases had recently traveled to states more heavily affected.

E. coli O157:H7 was first recognized as a cause of illness in 1982 during an outbreak of severe bloody diarrhea, in which the outbreak was traced to contaminated hamburgers. Infection often causes severe bloody diarrhea and abdominal cramps, but it can be nearly asymptomatic. There is usually little or no fever.

Young children and the elderly are at risk for hemolytic uremic syndrome, which can lead to kidney failure and sometimes death.