Diarrhea illness spreads across US, now reported in 31 states: What is cyclosporiasis and why are cases rising?

Published 11 July 2026 · us

A diarrheal illness caused by the microscopic parasite Cyclospora cayetanensis is spreading across the United States, with health officials reporting a sharp rise in infections

A diarrheal illness caused by the microscopic parasite Cyclospora cayetanensis is spreading across the United States, with health officials reporting a sharp rise in infections during the 2026 outbreak season. According to the US Centers for Disease Control and Prevention (CDC), 843 laboratory-confirmed domestically acquired cases of cyclosporiasis have been reported across 31 states as of July 9. The agency is also reviewing more than 1,500 additional suspected cases, meaning the actual number of infections could be significantly higher. Here's what you need to know. What is happening in the US? The CDC says several states have reported a noticeable increase in cyclosporiasis cases over the past two weeks compared with the same period last year. Key figures include 843 confirmed US-acquired cases 31 states reporting infections 86 hospitalisations Zero deaths More than 1,500 additional cases under review State and federal agencies, including the CDC and the US Food and Drug Administration (FDA), are investigating multiple outbreaks to identify the contaminated food sources responsible for the infections.

What is cyclosporiasis? Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis. People become infected after consuming food or water contaminated with human feces containing the parasite. Unlike many foodborne illnesses, Cyclospora is not usually spread directly from person to person because the parasite must remain in the environment for one to two weeks before it becomes infectious. What are the symptoms? Symptoms usually begin about one week after infection, although they can appear anywhere between two days and more than two weeks later. Common symptoms include Watery diarrhea Frequent or explosive bowel movements Loss of appetite Weight loss Stomach cramps Nausea Fatigue If left untreated, symptoms can last from several days to more than a month and may disappear before returning again. How does Cyclospora spread? The parasite spreads when people consume Contaminated fresh produce Contaminated drinking water Food handled under poor sanitary conditions Because Cyclospora requires time outside the human body to become infectious, direct contact with an infected person is considered unlikely to spread the disease.

Why are cases increasing? The CDC says cyclosporiasis follows a seasonal pattern in the United States. The outbreak season typically runs from May 1 through August 31, when infections linked to contaminated fresh produce are more commonly detected. Officials also note that reported case numbers may continue to rise because surveillance data typically lag by about six weeks. Who has been affected? Among the 843 domestic cases reported Patients ranged from 5 to 88 years old Median age: 44 years 59% were women 86 people required hospitalisation No deaths have been reported In addition, the CDC recorded 343 travel-related cases in people who became infected while outside the United States. How is the illness diagnosed? Doctors diagnose cyclosporiasis by testing stool samples. However, Cyclospora can be difficult to detect, and patients may need to submit multiple stool samples collected on different days. Healthcare providers must specifically request Cyclospora testing, as it is not included in routine stool examinations.