As cases of the parasite increase, here’s what Chicagoans need to know
As of July 16, Illinois had 277 cases statewide, including 23 hospitalizations and no deaths. That’s up from the 141 cases that the Illinois Department of Public Health (IDPH) reported the previous week. Check numbers daily at dph.illinois.gov/.
The rise isn’t unique to Illinois. Across 34 states, the Centers for Disease Control and Prevention (CDC) has confirmed 1,645 cases so far this year, along with 5,100 additional suspected cases under review. Michigan is seeing the worst of it, with more than 3,700 cases — the largest outbreak reported in the country. Within Chicago itself, the city has recorded as many as 50 cases, with the Chicago Department of Public Health (CDPH) stating that no single source or cause has yet been identified.
What is cyclospora, and how does it spread?
The microscopic parasite Cyclospora cayetanensis causes an intestinal illness called cyclosporiasis. People become infected by eating food (typically fresh produce) or drinking water contaminated with the parasite. Historically, public health officials have traced outbreaks in the United States to raspberries, basil, cilantro, snow peas, and leafy greens. Symptoms typically begin about a week after exposure but can appear anywhere from two days to more than two weeks later. They often include fatigue, loss of appetite, nausea, abdominal cramps, and watery diarrhea that can be frequent and, at times, explosive.
Steps to take now
While investigators continue to search for the source of the outbreak, health officials say it’s a good idea to be more cautious with leafy greens — and to shop for produce from local farmers, i.e. at farmers’ markets, if possible. The Michigan Department of Health and Human Services advises buying whole heads of lettuce or cabbage instead of bagged, prewashed products. Peel off and throw away the outer leaves, then wash the rest well. Rinsing alone may not remove the parasite, so when possible, cook leafy greens rather than eating them raw.
If you develop symptoms, particularly diarrhea lasting more than a few days, contact your physician. Antibiotics can treat the condition once testing confirms the diagnosis. Staying hydrated is also essential. Anyone unable to maintain fluid intake should seek emergency care.
Reporting a case
Cyclosporiasis is a reportable illness in Illinois, meaning physicians and laboratories are required to notify public health authorities of confirmed or suspected cases:
- Chicago residents/providers: Report to CDPH at (312) 743-9000 during business hours (after hours, call 311 and ask for the medical director on call) or review full reporting requirements at chicago.gov/cdph — Reportable Diseases
- Illinois-wide reporting: Contact your local health department or the IDPH Communicable Disease Section at (217) 782-2016 or go to the IDPH Cyclosporiasis page for the current health advisory and reporting guidance
Health officials note that true case counts are likely underreported, as most confirmed numbers reflect only people who sought care and were tested — making it especially important for anyone with prolonged, unexplained gastrointestinal symptoms to see a physician and get tested specifically for cyclospora. Not all labs automatically perform testing, unless requested.
Catherine Gianaro, a freelance writer and editor based in Chicago, has written about healthcare and higher education for more than three decades. With 90-plus awards in communications, she is well-versed in storytelling.
