Dec 13, 2006 (CIDRAP News) – A case-control investigation points to lettuce as the likeliest source of the Escherichia coli O157:H7 outbreak linked to Taco Bell restaurants, federal officials said today.
No contamination has been found in lettuce or other food items tested so far, but interviews with ill and well people who ate at the same Taco Bell restaurants, along with other information, point to lettuce, officials reported at a news conference this afternoon.
The case-control investigation also has suggested cheddar cheese and ground beef as possible sources of E coli, but the evidence is strongest for lettuce, said Christopher Braden, MD, a medical epidemiologist with the Centers for Disease Control and Prevention (CDC).
"We think that shredded lettuce consumed at Taco Bell restaurants in the northeastern states was the most likely source of the outbreak, given the information we have," Braden said. But he cautioned that the investigation is continuing and the conclusion is not final.
The case count in the outbreak increased by 4 today to 71, including 33 cases in New Jersey, 22 in New York, 13 in Pennsylvania, 2 in Delaware, and 1 in South Carolina, Braden reported.
He said 53 people were hospitalized and 8 had hemolytic uremic syndrome, a potentially fatal form of kidney failure. The patients fell ill between Nov 20 and Dec 6.
"Quite a lot" of other cases are under investigation, Braden said. "Some may be confirmed as part of the outbreak, and these numbers may increase in the next few days, but this doesn't necessarily mean the outbreak is ongoing." He said there have been no reports of new illnesses over the past few days.
The CDC and other agencies are working to trace where the lettuce came from, but officials declined to say which processing companies or growing areas are being investigated.
In a statement today, Taco Bell said it changed produce suppliers for the affected region on Dec 9 as a "strictly precautionary measure." The company also said all the cheese it uses is pasteurized and therefore is highly unlikely to be the source of contamination.
David Acheson, MD, of the Food and Drug Administration said there was no indication that the Taco Bell outbreak is connected with the E coli outbreak associated with Taco John's restaurants in Iowa and southern Minnesota. He declined to comment further on the Taco John's situation, saying the two states want to handle questions on that.
The Minnesota Department of Health today confirmed today that 5 E coli cases in Albert Lea and Austin involve the same DNA fingerprint as cases from the outbreak in Iowa. News reports have linked the latter with a Taco John's restaurant in Cedar Falls. The bacteria found in the Minnesota and Iowa patients do not match those from the East Coast outbreak, the MDH said.
Minnesota has 27 cases associated with the outbreak, including 5 confirmed ones, 1 "presumptive positive," and 21 probable cases still under investigation, the MDH said.
The Iowa outbreak has sickened at least 50 people, the Iowa Department of Public Health said today.