The Cyclospora parasite, which causes explosive diarrhea, is spreading across the globe at an alarming rate, with the World Health Organisation closely monitoring the situation. The United States has seen a significant surge in cases, with federal health officials working to identify the source of the microscopic parasite that triggers prolonged gastrointestinal illness as domestic cases rise for the summer season.
US Cases and CDC Response
The Centers for Disease Control and Prevention (CDC) reports nearly 200 cases of Cyclosporiasis across 17 states as of mid-June 2026. The main symptom is watery, often explosive diarrhea that can last for weeks or months without treatment. Individuals with compromised immune systems are more severely affected, experiencing abdominal cramping, bloating, nausea, fatigue, and significant weight loss.
The official outbreak season runs from May 1 through August, when warmer temperatures historically coincide with a spike in infections. The CDC notes that this summer's heatwave may be increasing infection numbers. New York has been hit hardest with 31 to 80 cases, followed by Texas and Illinois with 11 to 30 cases each.
Global Spread and European Impact
The parasite is now believed to have spread through travel, with 16 European countries affected. Health officials are monitoring numbers closely as the illness heads toward the UK. The full list of US states affected includes Alaska, Colorado, Connecticut, Florida, Georgia, Illinois, Louisiana, Massachusetts, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Texas, Virginia, and Wisconsin.
Treatment and Hospitalization
While the illness can resolve on its own, it often requires antibiotics. Severe cases may need hospitalization and a full course of antibiotics. In the US, about one-fifth of cases have required hospitalization. No deaths have been reported. Patients range from 5 to 86 years old, with a median age of 42; women account for 61% of cases.
The CDC, along with the Food and Drug Administration and state health officials, is investigating several multi-state clusters but has not yet identified the cause. "There is currently no evidence of a single, multistate Cyclospora outbreak linking all cases," the CDC noted in its surveillance report.
