Federal health officials are investigating the source of a microscopic parasite responsible for a growing number of prolonged gastrointestinal illnesses across the United States, as domestic cases continue to rise during the summer season.

The Centers for Disease Control and Prevention (CDC) has confirmed 145 cases of cyclosporiasis across 17 states as of mid-June 2026. All reported infections were acquired within the United States, prompting ongoing investigations into multiple possible sources.

The illness is caused by Cyclospora, a microscopic parasite that leads to cyclosporiasis. Its most prominent symptom is watery and often severe “explosive” diarrhea that can persist for weeks or even months if left untreated, according to the CDC. Other common symptoms include intense abdominal cramping, bloating, nausea, fatigue, and significant weight loss.

The CDC notes that cyclosporiasis typically peaks during its seasonal outbreak window from May 1 through August 31, when warmer weather conditions contribute to increased transmission.

Cases have been reported from several states, ranging from Texas to Alaska. New York currently has the highest number of reported infections, with between 31 and 80 cases. Texas and Illinois follow, each reporting between 11 and 30 cases.

While some infections may resolve without medical intervention, many require antibiotic treatment. Out of the 145 confirmed cases, 20 individuals have been hospitalized, according to CDC data. No deaths have been reported so far.

Patients affected range in age from 5 to 86 years, with a median age of 42. Women account for approximately 61% of reported cases.

The CDC, working alongside the Food and Drug Administration (FDA) and state health departments, is actively investigating several multi-state clusters. However, officials have not yet identified a single source linking all reported cases.

“There is currently no evidence of a single, multistate Cyclospora outbreak linking all cases,” the CDC stated in its latest surveillance update.