McHenry County health officials investigate fivefold rise in cyclosporiasis cases

The McHenry County Department of Health announced on Friday that it is investigating a sharp increase in cyclosporiasis cases in the county. Since June 25, officials have identified 61 cases, more than five times the number reported during the same timeframe in 2025. The investigation remains ongoing and the case count may change.

Cyclosporiasis typically produces watery diarrhea, loss of appetite, weight loss, stomach cramps, nausea, fatigue and low-grade fever about a week after exposure, and symptoms can persist for weeks. Health officials warned that prolonged diarrhea can lead to dehydration, advising anyone with reduced urination, dizziness or headache to seek medical care.

The illness is linked to contaminated fresh produce or water, with past outbreaks tied to leafy greens, herbs, snow peas, green onions and berries. No specific source has been identified in the current outbreak. The department urged residents to follow standard food-safety practices, such as rinsing fruits and vegetables under running water, scrubbing firm produce with a clean brush, and washing hands, utensils and surfaces thoroughly.

“With no specific food source identified, consumers can reduce, but not completely eliminate, their risk by carefully washing, preparing, and storing fresh produce,” the health department said.

Officials added that cooking produce to an internal temperature of 158°F is more effective than washing alone because it inactivates Cyclospora. The department will continue to monitor the situation and issue updates as more information becomes available.