A stomach-turning parasitic outbreak is spreading across the United States, and federal health officials are racing to find its source. The Centers for Disease Control and Prevention (CDC) has confirmed that 145 people ranging in age from 5 to 86 have been infected with the microscopic parasite Cyclospora cayetanensis between May 1 and June 16, 2026 — with 20 people hospitalized and cases now reported across 17 states. No deaths have been reported so far, but public health teams remain on high alert as investigations into the source continue.

The outbreak is concentrated most heavily in New York, which has reported between 31 and 80 confirmed cases — more than any other state in the country. Illinois and Texas each have between 11 and 30 cases, while Alaska, Colorado, Connecticut, Florida, Georgia, Louisiana, Massachusetts, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, and Wisconsin all have between one and 10 reported cases each. Public health teams are actively investigating several clusters of cases in New York, Illinois, and Texas simultaneously.

What Is Cyclospora — and Why Is This Outbreak Unusual?

Cyclospora cayetanensis is a microscopic intestinal parasite that causes cyclosporiasis, a nationally notifiable disease meaning healthcare providers are legally required to report confirmed cases to the federal government. The parasite infects the small intestine and causes a distinctive illness characterized by frequent, sometimes explosive watery diarrhea — a hallmark symptom that has made this outbreak particularly alarming for those affected.

What makes the current outbreak especially puzzling to investigators is that none of the 145 confirmed patients reported any international travel in the two weeks before becoming ill. Cyclospora infections in the US are typically linked to contaminated food or water consumed during travel to tropical or subtropical countries. The absence of any travel history strongly suggests a domestically contaminated food source with national distribution — but as of mid-June, the CDC and FDA have not yet identified the specific food product or supplier responsible.

Symptoms: What Cyclospora Infection Feels Like

Symptoms of cyclosporiasis typically appear about one week after exposure to the parasite and primarily affect the intestinal tract. The most commonly reported and recognizable symptom is frequent, explosive, watery diarrhea, but the full range of symptoms includes:

  • Loss of appetite and significant weight loss
  • Severe stomach cramping and bloating
  • Increased gas and nausea
  • Fatigue and low-grade fever
  • Vomiting, body aches, and headache (less common)

One of the most clinically significant aspects of a Cyclospora infection is its duration. Unlike typical food poisoning that resolves within a few days, cyclosporiasis symptoms can last anywhere from several days to a month or more if left untreated, increasing the risk of serious dehydration — particularly in young children, the elderly, and immunocompromised individuals. Critically, the infection does not spread from person to person, which means the only realistic path to infection is through consuming contaminated food or water.

What Makes Cyclospora So Difficult to Detect and Diagnose

One of the most significant challenges with this outbreak is that Cyclospora is frequently missed by both patients and physicians. The parasite is not part of a standard stool culture, and most clinical laboratories do not routinely test for Cyclospora unless it is specifically requested by the ordering physician. This means the true number of infected individuals is very likely far higher than the 145 confirmed cases currently in the CDC's data, as many patients may be suffering through symptoms without ever receiving an accurate diagnosis.

For those who do seek medical attention and receive a confirmed diagnosis, the standard treatment is a course of the antibiotic trimethoprim-sulfamethoxazole, sold under the brand names Bactrim, Septra, and Cotrim. Drinking plenty of fluids to prevent dehydration is also strongly recommended throughout the recovery period, particularly for children and older adults.

What Past Outbreaks Tell Us About the Likely Source

While the source of the 2026 outbreak has not yet been confirmed, the pattern of prior Cyclospora outbreaks in the US offers important clues. The parasite has a consistent seasonal cycle, with the CDC considering May 1 through August 31 the official cyclosporiasis season in the United States. Previous domestic outbreaks have repeatedly been linked to fresh produce items with national commercial distribution — particularly cilantro, basil, fresh raspberries, sweet peas, mesclun lettuce, and bagged salad kits. A 2019 outbreak was linked to basil imported from Mexico, while a high-profile 2018 outbreak was traced back to McDonald's salad products. The broad geographic spread of current cases across 17 states, with no obvious geographic concentration, is consistent with a contaminated product distributed through a major national supply chain.

For the most current outbreak data, case maps, and official guidance on cyclosporiasis prevention, the CDC's official Cyclospora resource page is being updated as the investigation progresses and is the most reliable source for real-time information.

How to Protect Yourself Right Now

Until investigators identify and remove the contaminated food source from the supply chain, health authorities recommend several practical precautions to reduce your risk. Thoroughly wash all fresh produce — particularly leafy greens, fresh herbs like cilantro and basil, and berries — before eating. Be especially careful with pre-washed or bagged salad products, which have been implicated in past outbreaks despite their "ready-to-eat" labeling. If you develop sudden watery diarrhea, cramping, nausea, or unexplained fatigue this summer — especially after eating salads or fresh produce — contact your doctor and specifically ask to be tested for Cyclospora, since the standard stool test will not detect it without a targeted request.