Authorities Identify Likely Source of Diarrhea-Causing Parasite

An estimated 2,640 cases caused by the Cyclospora parasite were reported in the state of Michigan as of July 13, up from 170 on June 30.

Juliette Fairley

Published: 7/14/2026, 2:03:04 PM EDT

Authorities Identify Likely Source of Diarrhea-Causing Parasite — Romaine lettuce. (Justin Sullivan/Getty Images)

Michigan health officials have identified a probable source of the state’s Cyclosporiasis outbreak.

The Michigan Department of Health and Human Services (MDHHS) conducted in-depth interviews with more than 1,000 infected individuals, and found that lettuce regularly emerged as a product they had consumed.

“Early information has shown lettuce as a common product that regularly comes up during the investigation,” MDHHS chief medical executive Dr. Natasha Bagdasarian said in a statement.

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

Cyclosporiasis is caused by a tiny parasite called Cyclospora in the intestines that causes watery, explosive, prolonged, or relapsing diarrhea.

An estimated 2,640 cases had been reported in Michigan as of July 13, up from 170 on June 30. Typically, Michigan only records between 40 and 50 cases of cyclosporiasis every year.

“Although we do not have a definite product identified as the source of the outbreak, we want to let Michiganders know what we have learned so far so they can take steps to protect their families,” Bagdasarian added.

As of July 9, there are an estimated 843 cyclosporiasis cases nationwide with 84 hospitalizations in 31 states, according to a U.S. Centers for Disease Control and Prevention (CDC) national surveillance tracker.

The CDC further noted that it is aware of more than 1,500 cases that require further analysis to confirm the illness as domestically acquired cyclosporiasis. The MDHHS advised that food items that have contributed to the spread of cyclosporiasis in the past include bagged salad mixes and kits, such as pre-cut lettuce blends with romaine, iceberg, red cabbage, and carrots, as well as fresh cilantro made of coriander leaves.

Fresh basil, raspberries, snow peas, and green onions, also known as scallions, are also on the MDHHS list of high-risk produce.

People contract cyclosporiasis by consuming food or water contaminated with the feces of an infected person that contains Cyclospora parasites, according to the UC Riverside School of Medicine.

The School’s public health epidemiologist and professor of medicine Brandon Brown contracted cyclosporiasis in 2018 during a trip overseas.

“I only ate at restaurants so did not have much control over my exposure, apart from washing my hands,” Brown said in a statement. “I could have been more selective at the places where I ate food, but I wanted to eat everything everywhere.”

Federal health officials advise those experiencing prolonged or relapsing diarrhea to see a health care provider and to specifically request a test for Cyclospora, because standard stool tests can miss the parasite.