Diarrhea-inducing parasite cases rise across US. What are risks in California?

A national outbreak of a foodborne parasite known to cause “explosive diarrhea” seems to have largely bypassed California, officials said.

However, health experts warned that statistics on the Cyclospora outbreak may be misleading.

“We believe there’s really an undercounting of the number of cases because not all cases are being tested,” said Dr. Dean Blumberg with UC Davis Health

Outbreaks of cyclosporiasis, a gastrointestinal illness caused by the parasite, have taken place in four Midwest states, with smaller outbreaks elsewhere, the U.S. Centers for Disease Control and Prevention said.

More than 400 cases have been confirmed in Michigan, Ohio, West Virginia and Kentucky, the CDC said.

“A specific food item has not yet been confirmed as the source,” the agency said.

But the Michigan Department of Health and Human Services reported more than 3,700 cases in the state as of Wednesday, July 15.

The department said leafy greens, such as lettuce, may be responsible for the outbreak there.

“However, other food items cannot be completely ruled out,” the agency said. “No specific type of produce, grower, or supplier has been identified as the source.”

Taco Bell has voluntarily stopped offering some ingredients at select restaurants in response to the outbreak, ABC News reported.

Here’s what you need to know:

Has the outbreak reached California?

The California Department of Public Health said cyclosporiasis cases in California remain within normal limits.

In fact, the number of reported cases in the state in 2026 is lower than at this time in 2025, the agency said.

From January to June, California has reported 41 provisional cases of cyclosporiasis, compared to 80 cases during the same period in 2025, the department said.

Typically, the state sees about 106 cases annually.

“We are aware of the outbreaks affecting other states, however, and are closely monitoring for any signs of local acquired infection,” said Dr. Erica Pan, department director and state public health officer. “We encourage Californians to protect themselves and their families by practicing safe food handling and thoroughly washing produce.”

What is Cyclospora?

Cyclospora is a foodborne parasite that “has been linked in the past to fresh produce such as herbs, salad greens and berries,” UC Davis Health said.

It can cause cyclosporiasis, a severe gastrointestinal illness.

“The hallmark symptom is watery, sometimes explosive, diarrhea,” UC Davis Health said. Other symptoms can include nausea, bloating and excessive gas.

It is not commonly associated with excessive vomiting or fever.

The parasite spreads through contaminated food, which can become infected when someone with the parasite and poor hand hygiene handles food.

Direct contact between people rarely results in the spread of the parasite, UC Davis said.

The parasite can be diagnosed with a stool sample and can be treated with an antibiotic.

What foods are commonly linked to Cyclospora?

UC Davis Health said foods often linked to the parasite include bagged or processed salad greens, basil, cilantro, parsley, raspberries, blackberries, snow peas and sugar snap peas,

How can you protect yourself against Cyclospora?

UC Davis Health recommends washing produce carefully before eating and choosing whole, unprocessed produce when possible.

Cooking fruits and vegetables before eating also can help prevent the spread of Cyclospora.

This story was originally published July 15, 2026 at 10:06 AM with the headline "Diarrhea-inducing parasite cases rise across US. What are risks in California?."