Cyclospora Outbreak Continues: Expert Explains Symptoms, Testing, and Prevention

Explosive diarrhea is spreading across Kentucky. The severe watery diarrhea can last a few days to more than a month. Untreated, it can relapse and cause long-term debilitating symptoms. It is caused by a single-celled parasite, Cyclospora. Similar to most illnesses, the elderly and immunocompromised are at higher risk of severe disease.

Although the outbreak has received increasing attention, understanding how public health agencies monitor these infections helps put the current situation into perspective. Forty-seven states mandate reporting of cyclospora infections. However, Federal reporting mandates were removed in July of 2025. My home state, Kentucky, requires reporting of Cyclospora within 1 business day. There were 67 cases in Kentucky between June 14 and July 2. About twice as many as Kentucky has in a typical year. Across the nation, 34 states have reported cases. By far, Michigan has been hit the hardest, officially reporting 5,002 cases, with 102 hospitalizations.

Despite these alarming numbers, finding the cause and source of this illness is a testament to the investigative acumen of public health epidemiologists.

Part of the challenge is that Cyclospora is difficult to test for; it is not detected on routine stool testing. Specific PCR testing or special microscopic techniques are required. The parasite may also shed intermittently, making the collection of multiple stool specimens often required. Similar to COVID-19, infections can be missed, and there may be a large gap between reported and confirmed cases, resulting in a quagmire of hard-to-reconcile statistics. As of July 13, the CDC has reported 1,645 confirmed cases and 141 hospitalizations, with another 5,100 cases under investigation.

Complicating matters further, cyclosporiasis can have an incubation period of up to 2 weeks, making it difficult to find the source. However, past outbreaks have been linked to uncooked vegetables, providing epidemiologists with a starting point. Only 440 cases were associated with foreign travel. Thus, the vast majority of infections were acquired within the United States. By far, the largest concentration of cases is in Southeastern Michigan.

Fortunately, investigators have made significant progress. Many of the cases were reported to be linked to Taco Bell. The iceberg lettuce supplied by Taylor Farms, an international agricultural produce supplier, is the leading culprit.

An important distinction. Diarrhea after eating Mexican food may now raise a red flag in many customers, but it is probably benign, especially if jalapenos were involved. Common peppers contain the chemical capsaicin, which makes them “hot” and irritates the gut, speeding transit. However, this type of diarrhea occurs within hours, not days later.

Even so, there is no reason for widespread alarm. The Washington Post has also reported that the cases in Indiana, Kentucky, Michigan, Ohio, and West Virginia are linked to those in Michigan by a single supplier of iceberg lettuce used at Taco Bell. Thus, it is unlikely that the local restaurants you frequent are involved in the outbreak.

Person-to-person transmission is extremely rare. Cyclosporiasis is not Ebola or COVID-19. Most people recover without sequelae. It is not a viral infection, and with treatment, the long-term complications of malabsorption and reactive arthritis are exceedingly unlikely. Treatment consists of a common, inexpensive, and readily available antibiotic, trimethoprim-sulfamethazine.

There is another important consideration. Similar to COVID-19, misinformation is starting to appear on social media. Some are recommending the anti-parasitic medication, ivermectin, for cyclosporiasis. Although it can treat head lice, rosacea, and intestinal threadworm infections, it is NOT effective against cyclosporiasis, nor does it cure cancer or COVID-19. Vaccines are not an issue, since none are available and are unlikely to be developed for an illness that is readily treated with an antibiotic, and can be prevented with public health elimination strategies.

What to do.

There are several practical steps people can take to reduce their risk.

• The current outbreak has been linked to salad greens. It is best to purchase heads of lettuce and to discard the outer 2 to 3 layers. And of course, thoroughly wash all raw produce.
• When possible, cook the produce to 158°F. Washing alone will not guarantee safety.
• Wash your hands with soap and water after handling raw produce.
• If you develop diarrhea that lasts longer than 3 to 5 days, seek medical attention sooner if you are medically frail, immunocompromised, or elderly.

From social media reports, even a mild illness may seem like an eternity to those afflicted. But in view of the relative infrequency of these infections and the treatments available, lifestyle changes are not warranted, except possibly installing a soft toilet seat and keeping plenty of soft toilet paper on hand.

One final thought: Support local farmers. During the initial stages of the outbreak, I all but ravaged my prize patio lettuce plant. Knowing where your food comes from is one of the best ways to avoid foodborne illnesses, especially in the age of decreased federal surveillance.