Cyclospora Outbreak Surpasses 1,000 Cases in Michigan

A widespread outbreak of cyclosporiasis caused by the microscopic parasite Cyclospora cayetanensis has grown to more than 1,000 confirmed cases across the United States, with the epicenter in southeastern Michigan. Health officials are racing to identify the source of the contamination as case numbers continue to climb.

According to AP News, Michigan alone has reported 992 confirmed cases as of July 8, with approximately 40 hospitalizations. Across the state line, Lucas County, Ohio, has reported 306 cases, and northwest Ohio has seen more than 500 cases total. The outbreak began around June 22 and has expanded at an alarming pace, with Michigan’s case count nearly 20 times the state’s typical annual average of roughly 50 cases.

What Is Cyclospora?

Cyclospora cayetanensis is a microscopic, single-celled parasite that infects the small intestine, causing watery diarrhea that can persist for weeks or months without antibiotic treatment. Unlike E. coli and salmonella, Cyclospora is spread only through human waste, not animal fecal matter. The parasite is transmitted when people ingest food or water contaminated with feces containing the parasite.

The CDC reports 843 domestically acquired cases across 31 states as of July 9, with illness onsets from May 1 through July 5. An additional 343 travel-associated cases have been reported. Nationally, 86 people have been hospitalized, and no deaths have been reported. Patients range in age from 5 to 88 years, with a median age of 44, and 59% are female.

Investigation Underway

Health officials have not yet identified a specific food, grower, or supplier as the source of the outbreak. Contaminated fresh produce is the leading hypothesis, as Cyclospora outbreaks in the U.S. have historically been linked to raspberries, basil, cilantro, snow peas, and salad mixes.

Dr. Natasha Bagdasarian, Michigan’s chief medical executive, told the Associated Press that “there is clearly a linked outbreak happening right now.” She noted that Michigan’s aggressive investigation and case-reporting infrastructure may be “part of the reason why this looks like a Michigan problem,” suggesting other states could be undercounting cases.

According to Food Safety News, the CDC data lags significantly behind state-level reporting due to a roughly six-week delay between illness onset and case confirmation. This means the true number of cases is likely higher than current official counts.

Challenges in Tracing the Source

Investigating Cyclospora outbreaks presents unique difficulties. Dr. Teena Chopra, a professor of infectious disease at Wayne State University, explained that symptoms typically appear one to two weeks after exposure, making it hard for patients to recall what they ate. Melanie Firestone, a foodborne illness researcher at the University of Minnesota, noted that standard food poisoning tests are often not designed to detect Cyclospora, leading to significant underreporting.

Adding to the complexity, technicians cannot grow the parasite in laboratory culture, making traceback from contaminated produce exceptionally difficult. Contaminated ingredients like basil or cilantro may be used in multiple recipes, further complicating efforts to identify a single shared exposure source.

Taco Bell Takes Precautionary Measures

In response to the outbreak, several Taco Bell locations have temporarily removed fresh produce items from their menus, including lettuce, pico de gallo, guacamole, cilantro, and onions, according to Food Safety News. The restaurant chain has posted notices at affected locations stating that all menu items remain available but are being served without those ingredients.

Public Health Guidance

Michigan health officials are urging residents to take precautions with fresh produce. Recommendations include buying whole heads of lettuce rather than prewashed bagged mixes, discarding outer leaves, and washing produce thoroughly under running water. However, experts caution that washing may not fully remove Cyclospora, as the parasite can cling to surfaces. Cooking vegetables to 158°F or higher is the most reliable way to kill the parasite.

Dianna Blau, the CDC’s acting parasitic diseases branch chief, told the Associated Press that there is “no evidence that the parasite has evolved to become more infectious.” However, thousands of cyclospora illnesses are reported in the U.S. each year, and experts attribute the general rise in cases over the past decade to climate change and better detection methods.

What to Watch For

As the investigation continues, officials expect case counts to rise further. The CDC’s surveillance data will be updated more frequently than in previous seasons. Anyone experiencing watery diarrhea that persists for more than a few days should consult a healthcare provider and ask specifically about Cyclospora testing, as standard stool panels may not detect the parasite. The infection is treatable with antibiotics, but without treatment, symptoms can persist for weeks.

Michigan residents in affected counties — particularly Monroe, Lenawee, Washtenaw, Wayne, and Oakland — should remain vigilant and practice enhanced food safety measures until the source of the outbreak is identified.