A diarrheal illness caused by the microscopic parasite Cyclospora cayetanensis is spreading across the United States, with health officials reporting a sharp rise in infections during the 2026 outbreak season.
According to the US Centers for Disease Control and Prevention (CDC), 843 laboratory-confirmed domestically acquired cases of cyclosporiasis have been reported across 31 states as of July 9. The agency is also reviewing more than 1,500 additional suspected cases, meaning the actual number of infections could be significantly higher.
Here’s what you need to know.
What is happening in the US?
The CDC says several states have reported a noticeable increase in cyclosporiasis cases over the past two weeks compared with the same period last year.
Key figures include:
843 confirmed US-acquired cases
31 states reporting infections
86 hospitalisations
Zero deaths
More than 1,500 additional cases under review
State and federal agencies, including the CDC and the US Food and Drug Administration (FDA), are investigating multiple outbreaks to identify the contaminated food sources responsible for the infections.
What is cyclosporiasis?
Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis.
People become infected after consuming food or water contaminated with human feces containing the parasite.
Unlike many foodborne illnesses, Cyclospora is not usually spread directly from person to person because the parasite must remain in the environment for one to two weeks before it becomes infectious.
What are the symptoms?
Symptoms usually begin about one week after infection, although they can appear anywhere between two days and more than two weeks later.
Common symptoms include:
Watery diarrhea
Frequent or explosive bowel movements
Loss of appetite
Weight loss
Stomach cramps
Nausea
Fatigue
If left untreated, symptoms can last from several days to more than a month and may disappear before returning again.
How does Cyclospora spread?
The parasite spreads when people consume:
Contaminated fresh produce
Contaminated drinking water
Food handled under poor sanitary conditions
Because Cyclospora requires time outside the human body to become infectious, direct contact with an infected person is considered unlikely to spread the disease.
Why are cases increasing?
The CDC says cyclosporiasis follows a seasonal pattern in the United States.
The outbreak season typically runs from May 1 through August 31, when infections linked to contaminated fresh produce are more commonly detected.
Officials also note that reported case numbers may continue to rise because surveillance data typically lag by about six weeks.
Who has been affected?
Among the 843 domestic cases reported:
Patients ranged from 5 to 88 years old
Median age: 44 years
59% were women
86 people required hospitalisation
No deaths have been reported
In addition, the CDC recorded 343 travel-related cases in people who became infected while outside the United States.
How is the illness diagnosed?
Doctors diagnose cyclosporiasis by testing stool samples.
However, Cyclospora can be difficult to detect, and patients may need to submit multiple stool samples collected on different days.
Healthcare providers must specifically request Cyclospora testing, as it is not included in routine stool examinations.
How can people protect themselves?
The CDC recommends several precautions to reduce the risk of infection:
-Avoid food or water that may be contaminated with feces.
-Wash hands thoroughly before eating or preparing food.
-Follow safe food handling and storage practices.
-Be especially cautious when travelling in tropical and subtropical regions.
What are authorities doing?
The CDC, FDA and state health departments are investigating multiple clusters of infections across several states to determine the food items responsible for the outbreak.
Officials are also using advanced laboratory tools to identify links between cases and trace the source of contamination.
