Michigan logged 3,762 cyclosporiasis cases on July 15, adding 453 in a day and extending its lead as the hardest-hit state in the U.S. outbreak.
State investigators suspect lettuce and other salad greens are driving the surge after interviews with more than 1,000 sick people, and officials urged residents to avoid pre-cut, boxed and bagged salad mixes.
CDC said 34 states have reported infections; as of July 13 it had counted 1,645 laboratory-confirmed cases, 141 hospitalizations and was investigating another 5,100 suspected cases.
About 400 confirmed cases in Michigan, Ohio, West Virginia and Kentucky have been linked to a likely common source, though CDC said no specific food has been identified yet.
Shiawassee County shows Michigan's highest rate at 307 cases per 100,000 people, underscoring how far the outbreak exceeds the state's usual roughly 50 cases a year.