The FDA has narrowed its investigation of the E. coli outbreak to the shredded lettuce served in meals at Taco Bell restaurants in northeastern states.

At press time, 71 cases of infection have been reported in five states: Delaware, New Jersey, New York, Pennsylvania and South Carolina (but the lone patient there ate at a Pennsylvania Taco Bell). The number of new cases has declined substantially, the CDC notes.

FDA investigators are further expediting their review of the fast-food chain’s records so they can trace the lettuce’s distribution channels and identify the farm(s) where the lettuce was grown, as well as all firms and facilities that handled the product between harvest and delivery.

So, is organic lettuce safe to eat?

The FDA has no indication that the lettuce served at any other restaurant or venue is connected to this outbreak. While another outbreak has been reported at Taco John’s restaurants in Iowa and Minnesota, the FDA is monitoring these cases, but the agency does not believe the two outbreaks are related. In fact, the CDC has officially stated “this outbreak was clearly linked to Taco Bell restaurants in the northeastern United States” and that shredded lettuce consumed at the locations in question is “the most likely source of the outbreak.”

Contamination “likely occurred before reaching the restaurants,” the CDC reports. “Health officials and the restaurant chain are working collaboratively to learn more about the shredded lettuce to determine how it may have become contaminated.”

While green onions were initially thought to be the culprit, confirmatory FDA tests did not indicate the presence of E. coli.

Map courtesy of the CDC