CDC investigates surge of cyclosporiasis cases across 18 US states

Public health authorities are monitoring a widening outbreak of cyclosporiasis, a parasitic intestinal infection that has surfaced in 31 states as of Monday, 13 July 2026. The illness, which causes severe, watery, and sometimes explosive diarrhea, is currently being investigated by the Centers for Disease Control and Prevention (CDC) in coordination with the Food and Drug Administration (FDA) and local health agencies.

While the CDC confirmed 843 cases between 1 May and 9 July, federal officials acknowledge the actual count is likely higher. The agency is currently analyzing more than 1,500 additional reports to determine if they qualify as domestically acquired cyclosporiasis. The disparity between federal data and state-level reporting is significant; for example, Michigan health officials reported 1,562 cases as of Friday, 10 July, marking a sharp deviation from the state's typical annual average of 50 cases.

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Understanding the Infection

Cyclosporiasis is caused by the microscopic parasite Cyclospora cayetanensis. According to the BBC and other reporting, the parasite is transmitted through the fecal-oral route, typically via the ingestion of water or produce contaminated with trace amounts of feces. The illness is not considered contagious between people, as the parasite requires time in the environment to mature into an infectious state after leaving the human body.

Symptoms usually appear between two days and two weeks after exposure. In addition to diarrhea, patients may suffer from nausea, fatigue, loss of appetite, stomach cramps, and low-grade fever. While many people with robust immune systems may recover without intervention, untreated infections can persist for months, with symptoms appearing to dissipate only to return in subsequent waves. Medical professionals typically treat confirmed cases with antibiotics.

Comparative Impact by State

Ongoing Investigations

Despite the high volume of illnesses, investigators have not yet identified a specific source, grower, or food item linked to the current surge. Dr. Caitlin Rivers of the Johns Hopkins Center for Health Security noted that contamination often occurs at the farm or irrigation level, which complicates efforts to trace specific food lots. Past outbreaks of cyclosporiasis have been linked to imported or domestically grown fresh produce, including raspberries, cilantro, basil, snow peas, and bagged salad kits.

Federal agencies maintain that there is no evidence of a single, nationwide outbreak connecting all cases. Instead, researchers are examining whether the current surge represents multiple, unrelated contamination events occurring simultaneously during the peak season for the parasite, which spans from May through August.

Prevention and Health Guidance

Public health experts suggest the following measures to mitigate risk:

• Thorough Washing: Rinse all fresh fruits and vegetables under running water, though officials caution that this method is not entirely foolproof against microscopic parasites.
• Thermal Processing: Cooking produce to at least 158 degrees Fahrenheit is considered an effective way to eliminate the parasite.
• Hand Hygiene: Wash hands thoroughly before and after handling raw produce to prevent cross-contamination in the kitchen.
• Clinical Consultation: Individuals experiencing persistent diarrhea or symptoms of dehydration should consult a healthcare provider. Testing is required for a definitive diagnosis.

As the investigation continues, officials at the CDC anticipate that case counts will continue to rise. This is partially due to an expected reporting lag, which can span up to six weeks between the initial onset of symptoms and the final tallying of confirmed data.