Illinois is reporting cases of Cyclospora this summer, with between 11 and 30 people sickened since the start of May as the CDC investigates several clusters across multiple states. The common source has not yet been identified.
The illness can cause watery diarrhea and frequent, sometimes explosive, bowel movements, and it can linger for weeks or even months if left untreated. That is why the current count matters now: only New York and Texas have reported similar or higher totals so far, putting Illinois among the states with the most reported cases while investigators still do not know what is linking them.
Cyclospora, also known as cyclosporiasis, is a parasitic illness that infects the small intestine and spreads when people ingest food or water contaminated with feces. Cases typically rise in spring and summer, and the annual season runs from May through August, which is the stretch when Illinois is now reporting illness.
The unresolved part is the one that matters most. The CDC, along with the FDA and state health departments, is still working several clusters at once, but it has not tied them to a single food or water source. Some people recover without treatment, but others can stay sick for weeks, and the CDC says people can be infected more than once and develop symptoms again.
For now, the best answer is also the simplest one: Illinois has a meaningful summer count, the investigation is active, and the source remains unknown. Until that changes, the warning for people in Illinois and elsewhere is to treat Cyclospora as a live outbreak, not a solved one.
