US Cyclospora Outbreak: Symptoms, Spread, and Prevention Explained

Health authorities in the United States are currently investigating a widespread Cyclospora outbreak, with hundreds of cyclosporiasis cases reported across at least 18 states this summer. Cyclosporiasis is an intestinal infection caused by the microscopic parasite *Cyclospora cayetanensis*. The illness is notably referred to as the 'explosive diarrhea parasite' due to its hallmark symptom of sudden, frequent, and often difficult-to-control watery diarrhea. As of mid-June 2026, the U.S. Centers for Disease Control and Prevention (CDC) officially reported 145 cases acquired domestically across 17 states, with 20 hospitalizations and no deaths. However, recent state-level data indicates a significant surge beyond these initial figures. Michigan, for instance, has seen an abnormally large and growing outbreak, with cases escalating to nearly 700 by July 7, far exceeding its typical annual average of approximately 50 cases. Similarly, New York has reported over 100 cases since May 1. When these state-specific surges are combined with the CDC's broader surveillance, the total number of infections across the U.S. is well over several hundred, potentially nearing 900 cases, reflecting a dynamic and evolving situation. The parasite spreads primarily through the consumption of food or water contaminated with feces containing *Cyclospora* oocysts. Unlike many other infections, direct person-to-person transmission is unlikely because the parasite needs time (at least one to two weeks) in the environment outside the body to become infectious after being passed in a bowel movement. Fresh produce, particularly fruits, leafy vegetables, herbs, and salad ingredients, are commonly implicated in past Cyclospora outbreaks because they are often eaten raw and can be contaminated during cultivation through irrigation water or soil. Past outbreaks in the U.S. have been linked to produce such as raspberries, basil, cilantro, snow peas, and mesclun lettuce. Symptoms of cyclosporiasis typically manifest within about seven days of exposure, though the incubation period can range from two to 14 days. Beyond the characteristic watery and often explosive diarrhea, infected individuals may experience other gastrointestinal symptoms including stomach cramps, nausea, bloating, increased gas, loss of appetite, fatigue, weight loss, low-grade fever, vomiting, and muscle aches. Without treatment, symptoms can persist for days, weeks, or even months, and may improve only to return later. While severe enough to cause hospitalizations, cyclosporiasis is rarely fatal, and no deaths have been reported in connection with the current outbreak. The recommended treatment for cyclosporiasis is a course of prescription antibiotics, commonly trimethoprim-sulfamethoxazole (Bactrim). Both the CDC and the U.S. Food and Drug Administration (FDA) are actively investigating multiple multistate clusters of cases to identify the contaminated food or water source. As of early July 2026, no single, definitive food source has been identified for all cases, indicating that there may be multiple contributing factors or clusters. The illness is nationally notifiable in 47 states, Washington D.C., and New York City, meaning healthcare providers are required to report confirmed cases, which is crucial for surveillance and outbreak investigation efforts. The cyclosporiasis season in the U.S. is generally considered to be from May 1 through August 31, aligning with the current surge in cases. To prevent infection, public health agencies recommend several food safety and hygiene practices. These include thoroughly washing hands with soap and water before preparing or eating food, rinsing fresh fruits and vegetables under running water, and scrubbing firm produce with a clean brush. Although rinsing may not eliminate all parasites, it can reduce the risk. Cooking fresh produce to at least 158°F (70°C) is effective in killing the parasite. Avoiding untreated water, especially when traveling to regions where Cyclospora is more common, is also advised. Individuals experiencing persistent diarrhea or other severe symptoms, particularly after consuming potentially contaminated food, should contact a healthcare provider for diagnosis and treatment.

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