Federal health officials are monitoring a growing number of cyclosporiasis cases this summer, with 145 infections reported across 17 states as of mid-June.
The Centers for Disease Control and Prevention says all 145 domestic cases involved people who became sick between May 1 and June 6, 2026 — and none had traveled internationally in the two weeks before falling ill.
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What is cyclosporiasis?
Cyclosporiasis is caused by a tiny parasite called Cyclospora cayetanensis, also known simply as Cyclospora. People become infected by consuming food or water contaminated with feces. While the illness can be unpleasant and prolonged, it is not usually life-threatening, according to the Centers for Disease Control and Prevention.
Signs, symptoms of cyclosporiasis
Not everyone infected with Cyclospora will feel sick. For those who do, the parasite targets the small intestine and typically causes watery diarrhea with frequent — and sometimes explosive — bowel movements.
Without treatment, the illness can last anywhere from a few days to more than a month. Symptoms may also appear to improve before returning, a pattern known as relapse.
What foods have been linked to U.S. outbreaks of cyclosporiasis?
Past cyclosporiasis outbreaks in the U.S. have been linked to raspberries, basil, cilantro, snow peas and mesclun lettuce. Although it’s unknown exactly how food and water become infected with Cyclospora, the Food and Drug Administration says people should be aware that rinsing or washing food is not likely to remove it.
2026 by the numbers
The CDC’s fast facts for the 2026 season paint a clear picture of the outbreak’s scope so far:
- 145 cases acquired in the United States
- 20 hospitalizations
- 0 deaths
- 17 states reporting cases
Sick individuals ranged in age from 5 to 86 years old, with a median age of 42. Roughly 61% of domestic cases were female. The median illness onset date was May 13, 2026.
How it spreads
Cyclospora spreads when people eat food or drink water contaminated with feces. One key detail sets it apart from many other infections: direct person-to-person transmission is unlikely.
That is because it takes at least one to two weeks outside the body for Cyclospora to become infectious after passing in a bowel movement.
Who is at risk?
Anyone can contract cyclosporiasis, but some people face a higher risk. Those living or traveling in tropical or subtropical regions — where cyclosporiasis is considered endemic, or regularly occurring — are more vulnerable.
In the U.S., outbreaks have been linked to various types of fresh produce. People can also be reinfected with Cyclospora more than once.
Those in poor health or who are immunocompromised may be at higher risk for severe or prolonged illness.
How cyclosporiasis is diagnosed
A healthcare provider can diagnose cyclosporiasis by testing a stool sample. However, detecting Cyclospora can be tricky — even in patients showing symptoms.
Standard stool testing does not typically include Cyclospora screening. Patients may need to submit multiple samples on different days, and providers must specifically request the specialized tests needed to identify the parasite.
Treating cyclosporiasis
Cyclosporiasis is treated with trimethoprim-sulfamethoxazole, sold under the brand names Bactrim, Septra or Cotrim. Those with a sulfa drug allergy should consult a healthcare provider about alternative options.
Regardless of treatment, the CDC says rest and staying well-hydrated are important — especially for those experiencing diarrhea. Most people with healthy immune systems will eventually recover without treatment, though the process can take a month or longer.
Preventing Cyclospora infection
Prevention comes down to two core habits: avoiding food or water that may be contaminated with feces and following safe food handling and storage practices. This is especially important when traveling in tropical or subtropical areas.
Investigations ongoing
Local, state and federal authorities — including the CDC and the U.S. Food and Drug Administration — are actively investigating several clusters of cases spanning multiple states. Officials have not yet identified a confirmed food source linked to the current outbreak.
The cyclosporiasis season runs May 1 through Aug. 31, though clusters have been detected outside that window in some years. Case counts historically rise during the spring and summer months.
Travel-related cases also reported
Beyond domestic infections, 45 additional cases involved people who became ill after eating or drinking contaminated food or water while traveling outside the United States.
Those individuals ranged in age from 17 to 89, with a median age of 43, and 62% were female. Three of the 45 were hospitalized. No deaths were reported in this group.
What to do if you’re sick
Anyone experiencing symptoms consistent with cyclosporiasis is encouraged to contact a healthcare provider. The illness is treatable, and early reporting helps officials detect and contain outbreaks more quickly.