Cause of E coli outbreak still elusive as cases mount

Dec 12, 2006 (CIDRAP News) – The cause of an Escherichia coli O157:H7 outbreak linked to Taco Bell restaurants remained elusive today as the number of cases increased to 67 in 5 states, according to federal officials.

Taco Bell pulled green onions from all its restaurants last week after preliminary tests by an independent lab indicated contamination in a few samples. But an update by the Centers for Disease Control and Prevention (CDC) said those tests have not been confirmed, and the overall investigation by federal and Taco Bell is "demonstrating that onions of any type are probably not linked to this outbreak."

The CDC said 67 E coli cases have been associated with Taco Bell, an increase of 3 since yesterday. The cases include 30 in New Jersey, 22 in New York, 12 in Pennsylvania, 2 in Delaware, and 1 in South Carolina. The New York Times reported today that as many as 300 cases related to the outbreak are suspected.

Of the 67 patients, 51 (76%) were hospitalized, and 8 (13%) developed hemolytic uremic syndrome, a type of kidney failure that can be fatal, the CDC said. E coli isolates from 47 of the 67 patients have been matched to the outbreak strain by PulseNet, an electronic network for sharing DNA fingerprinting (pulsed-field gel electrophoresis) data.

A sample collected Dec 4 from an open bin of chopped yellow onions at a Taco Bell in Nassau County, N.Y., tested positive for E coli O157:H7, but the CDC said that strain's genetic fingerprint did not match the outbreak strain. "The pattern of the chopped onion strain has not been seen before in the PulseNet database," the CDC said.

Though the testing of other food items is ongoing, no preliminary or confirmatory tests have linked any other food to the outbreak, the CDC said. The FDA has said that until the food source is identified, the risk to the public is ongoing.

Meanwhile, health officials in Iowa and Minnesota are investigating a possible E coli O157:H7 outbreak that appears to be linked to Taco John's, another fast food chain.

In a Dec 8 press release, the Black Hawk County, Iowa, Department of Health announced that 19 cases of apparent E coli infection had been reported and that 14 patients were hospitalized. County officials said they were awaiting final stool culture results.

The county news release didn't identify the restaurant involved, but a report today in the Des Moines Register said it is a Taco John's in Cedar Falls, Iowa. That report said 18 people have been hospitalized in the outbreak.

The Minnesota Department of Health (MDH), in a press release yesterday, said healthcare providers in two southern Minnesota towns reported an increase in patients with bloody diarrhea, a hallmark of E coli O157:H7 infection. Samples from several of the patients were positive for E coli on preliminary tests.

Three of the patients said they ate at the Taco John's in Albert Lea between Nov 30 and Dec 2, within the same time frame as the outbreak in Iowa.

"We do not yet know whether these cases in Minnesota are actually linked to any cases in Iowa," said Kirk Smith, MD, foodborne disease investigation supervisor for the MDH. (Albert Lea is about 120 miles from Cedar Falls.) Though genetic fingerprinting to see if the outbreak strains match won't be completed for 2 more days, he said the MDH wanted to make residents aware of the investigation.

So far, there is no evidence that the outbreaks in Iowa and Minnesota are related to the Taco Bell outbreak in the Northeast, Smith said.

In other food outbreak news, the FDA announced today that it is investigating a norovirus outbreak linked to frozen raw oysters on the half shell from South Korea. Eight people became ill with the virus after eating the oysters at a private event in Woodburn, Ore. The FDA tested the oysters, and on Dec 8, samples from the same production lot tested positive for norovirus.

The source of the contaminated oysters is Central Fisheries Company in South Korea. They were imported by California-based Fortuna Sea Products, Inc., and were distributed in Texas, Colorado, Nevada, California, and Oregon. Fortuna Sea Products recalled the oysters Nov 27.

The CDC has said that norovirus is the leading cause of foodborne illness in the United States. Symptoms, including nausea, vomiting, diarrhea, and stomach cramps, usually occur within 48 hours of exposure to the virus and last 1 to 2 days, the FDA said.

See also:

Dec 12 CDC update on E coli outbreak

Dec 12 FDA press release on oyster-related norovirus outbreak

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