:What has made the cyclospora behind the US outbreak

Cyclospora, the parasite behind thousands of suspected U.S. cases of a foodborne illness, has a long incubation period, and samples cannot be cultured in labs, making it especially challenging to trace.



To investigate, laboratory scientists have worked with epidemiologists to gather information from infected patients about what they ate, where and when, and then the U.S. Food and Drug Administration has tried to identify the tainted food products.



From those interviews, public health officials have traced a large outbreak in Michigan, Indiana, Kentucky, Ohio and West Virginia to shredded iceberg lettuce from Taco Bell restaurants supplied by Taylor Farms' operations in Mexico.



The officials often must rely on those interviews instead of testing because of the particular characteristics of cyclospora.



The FDA did test Taylor Farms' product at the U.S.-Mexican border — aimed at preventing more tainted produce from entering the United States.



Even so, Taco Bell accounts for only about 60% of all cases in the multistate outbreak, Investigations of other, possibly unrelated outbreaks are still underway, according to the U.S. Centers for Disease Control and Prevention.