Diarrheal disease spreads across US, now reported in 31 states: What is cyclosporiasis and why are cases on the rise?

A diarrheal disease caused by the microscopic parasite Cyclospora cayetanensis is spreading across the United States, with health officials reporting a spike in infections during the 2026 outbreak season.

According to the US Centers for Disease Control and Prevention (CDC), as of July 9, 843 laboratory-confirmed domestic cases of cyclosporiasis had been reported in 31 states. The agency is also reviewing more than 1,500 other 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 to the same time last year.

843 confirmed cases acquired in the US

31 states report the infection

More than 1,500 other cases are 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 disease 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 becoming 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.

Frequent or explosive bowel movements

If left untreated, symptoms can last from a few days to more than a month and may disappear before returning again.

How is cyclospora spread?

The parasite is spread when people consume:

Contaminated fresh produce

Contaminated drinking water

Food is handled under poor hygienic 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 period usually runs from May 1 to August 31, when infections associated with contaminated fresh produce are more frequently detected.

Officials also note that reported case numbers may continue to rise because tracking data typically lags by about six weeks.

Who was affected?

Among the 843 reported domestic cases:

Patients ranged in age from 5 to 88 years

86 people required hospitalization

No deaths were reported

In addition, the CDC has recorded 343 travel-related cases of people who contracted the virus outside the United States.

How is the disease 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.

Health care providers must specifically request testing for Cyclospora, as it is not included in the routine stool examination.

How can people protect themselves?

The CDC recommends several measures to reduce the risk of infection:

– Avoid food or water that may be contaminated with feces.

– Wash your hands thoroughly before eating or preparing food.

– Follow the principles of safe food handling and storage.

-Be especially careful when traveling in tropical and subtropical areas.

What are the authorities doing?

The CDC, FDA and state health departments are investigating numerous clusters of infections in several states to determine the foods responsible for the outbreaks.

Officials are also using advanced laboratory tools to identify links between cases and trace the source of contamination.