A major parasitic infection outbreak is sweeping the United States, causing severe gastrointestinal illness and hospitalizations.

The U.S. Centers for Disease Control and Prevention reports at least 20 people across 17 states have been hospitalized. More than 1,000 cases of cyclosporiasis have been confirmed nationwide.

The worst-hit state is Michigan, with the Michigan Department of Health and Human Services reporting 1,251 cases as of July 9. Officials confirm this is the largest cyclosporiasis outbreak in the state's history.

The CDC and the Food and Drug Administration are actively investigating several illness clusters in Illinois, New York, Pennsylvania, and Texas. The source of the contamination is under urgent investigation.