Outbreak of diarrhea from parasite expands to more states as US cases soar beyond last year's level

There have been 1,645 confirmed cases of cyclosporiasis acquired in the United States since May 1, and more than 5,100 additional cases are being investigated, the US Centers for Disease Control and Prevention said Tuesday -- a sharp increase in cases compared with recent years.

Since May 1, cases have been identified in 34 states. Federal health officials said there are multiple investigations underway, some tied to the large outbreak in the Midwest, some involving single states and some involving cases not yet tied to any cluster.

Cyclospora activity tends to increase during the spring and summer, but the number of confirmed cases since May 1 is already more than six times higher than it was by this time last year, according to a health alert sent by the CDC. If the more than 7,000 possible cases that are confirmed or under investigation are included, this year's total is 27 times higher than last year's total at this time.

"This is much, much higher than what we've seen last year or the year before," said Dr. Gwen Biggerstaff, deputy director of the CDC's Division of Foodborne, Waterborne, and Environmental Diseases, calling it "a very big shift" from previous seasons.

About 1 in every 11 cases has been hospitalized, according to data available to the CDC. No deaths have been reported.

An additional investigation notice published by the CDC on Tuesday notes that at least 400 cases across at least four states -- Michigan, Ohio, West Virginia and Kentucky -- "appear to be epidemiologically linked, suggesting that there could be a common source of these infections."

The Michigan state health department has reported more than 3,300 cases of cyclospora during the outbreak investigation. Michigan said it has interviewed more than 1,000 people as part of its investigation, and current results suggest that lettuce or salad greens may be a potential source for the outbreak. However, the state said it hasn't ruled anything out. "No specific type of produce, grower or supplier has been identified as the source," the state said.

Fast food chain Taco Bell said Tuesday that it was removing some ingredients from its menu at some restaurant locations as a precaution. "Public health officials have not confirmed a link to Taco Bell or any specific ingredient, supplier, restaurant or retailer," Taco Bell Corp. said in a statement. "While authorities continue their broader review, Taco Bell has voluntarily and temporarily removed limited ingredients at select restaurants as a precautionary measure."