By John Brhel
July 16, 2026
People across the United States are taking a closer look at their lettuce and leafy greens this summer thanks to an outbreak of cyclosporiasis, a gastrointestinal illness that causes several symptoms, the most notable being severe, watery diarrhea
According to the Centers for Disease Control and Prevention, there are 1,645 confirmed cases across 34 states, with over 5,100 additional cases requiring further analysis. And the illness has hit our own state, with reports in New York City
The illness can affect anyone, but who is most at risk? We spoke withAzadeh Nasuhidehnavi, an infectious disease expert and Assistant Professor of Pharmaceutical Sciences at Binghamton University, about what causes the illness, who is likely to be hit the hardest, and how to stay safe
What causes cyclosporiasis?
Nasuhidehnavi: Cyclosporiasis is caused by a microscopic, single-cell parasite called Cyclospora cayetanensis. It spreads through food (it has been linked to fresh produce) or water contaminated with the parasite’s oocysts, the resistant microscopic form of the parasite that survives outside the body and causes infection when ingested.
Because oocysts need certain temperatures and moisture for maturation, high numbers of infection mostly occur during spring and summer.
What are the symptoms of cyclosporiasis?
Symptoms include watery diarrhea (often explosive), cramping, nausea, fatigue, and occasionally low-grade fever, typically appearing 7 to 10 days after exposure and lasting around two weeks if untreated.
Does cyclosporiasis affect some people more severely than others?
Not everyone gets equally sick, and a growing body of research points to a few consistent risk factors that explain why.
The most important determinant is the status of an individual’s immune system. For most healthy adults, cyclosporiasis is unpleasant but self-limited.
Immunocompromised groups, including transplant recipients, cancer patients on chemotherapy, dialysis patients, and people living with HIV/AIDS, face substantially higher infection rates and more severe, prolonged illness.
Is age a risk factor?
Yes. Infants and young children, whose immune systems are still developing, and the elderly, whose immune defenses naturally wane, tend to experience more severe or prolonged symptoms than healthy young adults.
This is consistent with patterns seen in related parasitic gut infections like cryptosporidiosis, where children under 5 years old make up the large majority of cases in several recent outbreaks
What should people at risk do to stay safe?
For the immunocompromised, the very young, and the elderly, it can be far more serious, which is why health officials are urging clinicians to maintain a high index of suspicion in these groups as the outbreak investigation continues, and why produce safety and handwashing remain the front line of prevention while the
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