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More than 11,500 cases of cyclosporiasis have been reported in 41 states, according to the Centers for Disease Control and Prevention (CDC) on Wednesday (July 22). The CDC states that at least 4,173 cases are laboratory-confirmed, with 308 hospitalizations, and an additional 7,400 cases under investigation. Many of these have been reported by Michigan and Ohio, marking one of the largest outbreaks of this foodborne parasite in recent U.S. history
The CDC has issued a formal health alert as cases have surged well above last year’s numbers, with some clusters showing strong links among patients from Michigan, Ohio, West Virginia, and Kentucky. According to reporting from AJMC, Michigan alone has confirmed more than 1,500 cases with 44 hospitalizations as of July 10. Lucas County, Ohio, has also reported over 300 cases. State officials note that the number of infections is rising quickly, and Michigan’s Department of Health and Human Services has conducted over 1,000 patient interviews.
The parasite, Cyclospora cayetanensis, causes cyclosporiasis, an intestinal illness that leads to watery diarrhea, cramping, nausea, fatigue, and sometimes weight loss. Symptoms can begin two days to two weeks after exposure and may persist for weeks if untreated. The standard treatment is trimethoprim-sulfamethoxazole, but some people recover without medication. The parasite is not spread person-to-person; instead, it is contracted by consuming contaminated food or water, often produce exposed to feces-contaminated irrigation water, as explained by Infection Control Today.
CDC officials and state public health leaders are investigating possible sources, with lettuce and salad greens under scrutiny, though a specific food item has not been confirmed. The Food and Drug Administration (FDA) is also investigating and will intervene if a contaminated food source is identified.
The CDC recommends following food safety measures, such as washing produce thoroughly and choosing whole heads of lettuce instead of pre-washed bags. Standard disinfectants do not kill Cyclospora, so careful cleaning and handwashing with soap and water are critical.
Officials urge clinicians to order specific tests for Cyclospora when patients present with unexplained diarrhea and to report cases quickly. The CDC expects cyclosporiasis season to continue through August. The investigation into the source of the outbreak is ongoing, and public health agencies will update their guidance as new information emerges.