What You Need to Know About the Cyclospora Outbreak Spreading Across the U.S.

A parasitic illness known for causing explosive, watery diarrhea is surging across the United States at rates that are already far exceeding last year’s totals, and public health officials are racing to identify the source. Here is what patients need to know about cyclosporiasis, the illness caused by the microscopic parasite Cyclospora cayetanensis, and what to do if you think you may be infected.

What Is Cyclospora and How Does It Spread?

Cyclospora cayetanensis is a microscopic parasite that causes a gastrointestinal illness called cyclosporiasis. It spreads through food or water that has been contaminated with feces containing the parasite. It is not passed directly from person to person. The illness typically peaks in late spring and summer, when warmer temperatures historically coincide with a spike in infections, and the official outbreak season, according to the Centers for Disease Control and Prevention (CDC), runs from May 1 through August 31.

Past outbreaks have frequently been linked to contaminated fresh produce, particularly raspberries, basil, cilantro and salad mixes. Contamination typically occurs at the farm or irrigation level, which makes identifying a source difficult and time-consuming.

How Bad Is the Current Outbreak?

The numbers tell a striking story. The United States typically reports around 2,700 cases of cyclosporiasis in an entire year. As of July 13, 2026, more than 4,000 cases have already been reported nationally, according to state health department data, with the CDC confirming 843 cases from 31 states as of July 9.

Michigan has been hit hardest. The state reported more than 3,300 cases since the end of June alone, a number roughly 50 times higher than the state’s annual average of 40 to 50 cases, with approximately 44 requiring hospitalization. Ohio has reported at least 364 cases in 2026, with a significant surge occurring since late June. New York has identified approximately 500 cases, and additional clusters have been identified in Texas, Illinois, Pennsylvania and other states.

The CDC has said it currently has no evidence of a single multistate outbreak linking all cases and is actively monitoring clusters across multiple states. Investigators have noted that affected individuals did not report international travel in the 14 days before becoming ill, which strongly points to a domestic food source.

What Are the Symptoms?

The hallmark symptom of cyclosporiasis is watery, often explosive diarrhea with frequent bowel movements that can persist for weeks or even months if the infection goes untreated. Additional symptoms include severe abdominal cramping, bloating, nausea, fatigue, loss of appetite and significant weight loss. Some people also develop a low-grade fever, though that is less common.

One important clinical note: Cyclosporiasis is frequently misdiagnosed. Its symptoms closely resemble irritable bowel syndrome and colon inflammation, and standard stool sample tests do not reliably detect the parasite. Specific testing for Cyclospora cayetanensis must be requested explicitly, so if you are experiencing these symptoms, it is important to ask your doctor about testing for this specific parasite rather than assuming a standard stool panel will catch it.

Who Is at Risk?

Anyone who consumes contaminated food or water can become infected. There is a higher risk of infection in tropical and subtropical regions, where the parasite is more common, but the current outbreak is affecting people who have not traveled internationally, meaning the source is domestic. The illness is not typically life-threatening for otherwise healthy adults, but symptoms can be severe and prolonged, and some cases have required hospitalization.

How Is It Treated?

Cyclosporiasis is treatable. The standard treatment is a course of the antibiotic trimethoprim-sulfamethoxazole, commonly known as Bactrim or Septra. Without treatment, symptoms can last anywhere from a few weeks to several months, with many patients experiencing a relapsing pattern of feeling better followed by feeling worse again. Staying hydrated is important, particularly given the severity and duration of diarrhea associated with the infection.

What Should You Do?

If you are experiencing prolonged watery diarrhea, fatigue and abdominal cramping, particularly if you have recently consumed fresh produce, contact your health care provider and specifically request testing for Cyclospora. Do not assume you will test positive on a standard stool panel. In the meantime, wash all fresh produce thoroughly, follow CDC guidance on food safety and stay alert to any recalls or advisories linked to this outbreak as investigators continue to identify the source.