Health officials are tracking a growing outbreak of cyclosporiasis that has spread across multiple states, with sharply higher case counts in Michigan and Ohio and investigators still searching for the source.
More than 1,000 cases have been reported in Michigan and over 500 in Ohio, marking one of the largest spikes in recent memory. Officials call this the largest cyclosporiasis outbreak in Michigan’s history, and public health teams are working around the clock to identify where the infections began. No deaths have been reported so far, but the sheer number of sick people has pushed local agencies into high-alert mode.
MYSTERY PARASITE LEAVES AMERICANS BATTLING ‘EXPLOSIVE’ ILLNESS AS CDC INVESTIGATES This parasite causes long bouts of watery diarrhea that can last for weeks if not treated, and the symptom profile has alarmed patients and doctors alike. The CDC noticed an uptick in mid-June and case counts have climbed steadily since, with dozens of states now reporting illnesses tied to the parasite.
Michigan announced a cluster after identifying more than 170 cases in the southeastern part of the state since June 22, a huge jump from the usual annual count of around 50 cases. Similar reports have surfaced in 28 other states, and Ohio has seen a significant rise right across the border. Texas and several other states have also reported dozens of infections as investigators try to trace common exposures.
The signature symptom of cyclosporiasis is watery, often “explosive” diarrhea, and infections can bring other nasty effects like severe abdominal cramping, bloating, nausea, fatigue and noticeable weight loss. While some people clear the infection on their own, many require targeted antibiotic therapy to recover fully. Health officials emphasize testing and prompt treatment when symptoms suggest this parasite.
Investigators with the CDC, the Food and Drug Administration and state public health departments are probing multiple multistate clusters but have not yet pinpointed a single source. Historically, outbreaks have been linked to contaminated fresh produce or irrigation water, which makes tracing particularly tricky when ingredients move through long supply chains. Washing produce helps reduce risk, but it does not eliminate the possibility of contamination entirely.
There is a defined outbreak season for this parasite that runs from May 1 through Aug. 31, and warmer weather patterns during that window often coincide with higher transmission. That seasonal pattern gives investigators a timeframe to focus on and helps public messaging about safer handling and preparation of fresh fruits and vegetables. Still, the current spread across many states means people should pay closer attention to symptoms and food safety steps this summer.
Officials in Michigan have urged shoppers to avoid pre-washed, bagged lettuce and instead opt for salad mixes or whole heads of lettuce, removing two to three outer leaves before washing, and cooking vegetables when possible. Those steps lower, but do not eliminate, the chance of exposure because contamination can occur before produce reaches consumers. Public health guidance also stresses that anyone with persistent gastrointestinal symptoms seek medical evaluation and testing.
The investigation remains active and evolving, with health departments sharing data as new cases are reported and possible links emerge. In the meantime, practical precautions—thoroughly washing produce, being cautious with ready-to-eat salads, and getting prompt care for severe diarrhea—are the best tools individuals have to reduce risk. Officials continue urging vigilance while they follow leads to find the source of this widespread outbreak.
