Parasitic Diarrhea Illness Spreads Across 17 US States: What You Need to Know

A parasitic infection called cyclosporiasis is causing a surge of gastrointestinal illness across more than 17 U.S. states as of mid-June 2026, with health officials warning consumers to exercise caution with fresh produce ahead of the July Fourth holiday weekend. The parasite, Cyclospora cayetanensis, typically spreads through contaminated food and is known for causing "explosive" diarrhea and other stomach distress. The Centers for Disease Control and Prevention (CDC), along with state and federal health agencies, are actively investigating the outbreak as cases continue to mount during the peak cyclosporiasis season.

Outbreak Overview and Current Case Count

As of June 16, 2026, the CDC and state health departments have documented 145 confirmed cases of cyclosporiasis contracted within the United States. An additional 45 cases were reported among individuals who became ill while traveling abroad. Of the 145 domestic infections, 20 patients required hospitalization, though no deaths have been reported to date.

The outbreak spans individuals ranging in age from 5 to 86 years old, with a median age of 42 years. Michigan has emerged as a particularly hard-hit state, with case numbers already tripling compared to the entire 2025 total. Health officials note that while clusters of cases are under investigation, no single multistate outbreak linked to a common food source has been definitively identified at this time.

What Is Cyclosporiasis and How Does It Spread?

Cyclosporiasis is a parasitic gastrointestinal infection caused by the microscopic parasite Cyclospora cayetanensis. The infection typically occurs when individuals consume food or water contaminated with the parasite. Fresh produce, including fruits and vegetables, is the most common source of infection.

The primary symptom is watery, frequent, and sometimes explosive diarrhea, which can be accompanied by nausea, vomiting, loss of appetite, bloating, stomach cramps, fever, and extreme fatigue. Symptoms typically develop within days of parasite exposure and can persist for several weeks if left untreated. The CDC emphasizes that the infection is preventable through proper food handling and sanitation practices.

Seasonal Timing and Risk Period

Cyclosporiasis cases in the United States typically spike during a predictable seasonal window. The CDC identifies May 1 through August 31 as the peak months for cyclosporiasis transmission, a pattern referred to as the cyclosporiasis "season." The current 2026 outbreak aligns with this seasonal pattern, emerging just as consumers increase their consumption of fresh summer produce and outdoor food preparation ahead of Independence Day celebrations.

Health officials recommend heightened vigilance during this four-month period, particularly when purchasing and preparing fresh fruits and vegetables. The timing of the outbreak serves as a reminder that holiday weekends and outdoor gatherings often coincide with peak parasite transmission risk.

CDC and Government Response

The CDC, the Food and Drug Administration (FDA), and state health authorities are actively investigating the outbreak to identify potential common sources and contain further spread. According to a CDC statement from June 2, the agency is tracking surveillance data across all U.S. states and is investigating multiple clusters of cases in coordination with the FDA. However, as of the latest reports, investigators have not isolated a single multistate outbreak with a definitively linked common source.

Agencies are urging the public to practice enhanced food safety measures, including thorough washing of fresh produce under running water, proper storage of perishables, and careful food handling during meal preparation.