For weeks, the U.S. has been dealing with an unpleasant public health mystery. The cyclospora parasite has infected thousands of people across the country. The largest cluster of cases is in Michigan and other midwestern states, not including Minnesota.

The Food and Drug Administration tracked the outbreak to a lettuce farm that supplies Taco Bell. Taylor Fresh Foods, the lettuce company, recalled several of its salad mix products. But the case isn’t closed, exactly.

MPR News host Nina Moini spoke with Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, about the parasite and the public health response.