Recent days have seen a surge in cyclosporiasis cases across the United States, a parasitic illness known for causing severe, watery diarrhea. Michigan is experiencing an unprecedented outbreak, reporting nearly 1,000 cases—far exceeding its typical annual average of 50 and making it the state’s largest recorded outbreak. Ohio has also witnessed a sharp rise, with 177 cases documented as of July 2, according to state health data.
The U.S. Centers for Disease Control and Prevention (CDC) has confirmed 145 cases across 17 states as of June 16, though this figure is likely an undercount due to delayed reporting. While no deaths have been linked to the current outbreak, some individuals have required hospitalization, highlighting the illness’s potential severity.
What is cyclosporiasis?
Cyclosporiasis is a gastrointestinal infection caused by the Cyclospora parasite, which is transmitted through consumption of raw produce or water contaminated with human fecal matter. In the U.S., it is a seasonal condition, with outbreaks most common during summer months (May–August). Historical cases have been linked to contaminated fruits, vegetables, and herbs like basil, cilantro, berries, and spinach.
The CDC describes the hallmark symptom as watery diarrhea with frequent, sometimes explosive bowel movements. Additional symptoms include abdominal cramps, nausea, fatigue, loss of appetite, low-grade fever, and vomiting. These symptoms can persist from several days to over a month, and some individuals remain asymptomatic. The incubation period averages about seven days but can range from two days to two weeks.
While rarely life-threatening, the illness can significantly impact quality of life. Most recover without medical intervention, though those with compromised immune systems face greater risks. Antibiotics are typically prescribed for treatment.
How does this compare to previous U.S. outbreaks?
Past U.S. outbreaks often stemmed from produce contaminated via fecal-laden irrigation water. A 2022 Florida outbreak linked to packaged salad kits caused hundreds of illnesses, while larger historical incidents include a 1996 raspberry-related outbreak (1,500 cases) and a 2019 Mexican basil outbreak (2,400 cases across the U.S. and Canada).
How can you protect yourself from cyclosporiasis?
Preventing infection requires avoiding potentially contaminated food or water. Thoroughly washing fresh produce is critical, though some foods—such as raspberries, blackberries, lettuce, spinach, cilantro, green onions, and basil—are harder to clean due to their texture. Consumers are advised to opt for whole heads of lettuce over pre-washed varieties and discard outer leaves before washing.
Cooking fruits and vegetables when possible can also eliminate the parasite. Health officials emphasize caution as they investigate the source of the current outbreak.
