Michigan links a growing Cyclospora outbreak to lettuce and salad greens
Michigan health officials say early evidence points to lettuce or other salad greens as a potential source of a rapidly expanding outbreak of cyclosporiasis, a parasitic illness that causes frequent watery diarrhea. The investigation remains open, and officials have not identified a specific type of produce, grower or supplier.
The Michigan Department of Health and Human Services cautioned that other food sources cannot yet be ruled out. The preliminary finding is therefore not a recall of a named product, but it gives investigators a direction for comparing what sick people ate and tracing food through restaurants, stores and suppliers.
Case counts have risen sharply
Michigan reported 1,562 cases between June 22 and July 10, with 44 people hospitalized. By Monday, the state was reporting 2,640 cases. Ohio, which borders Michigan, was reporting another 177 cases, bringing the two states’ reported total to 2,817.
Michigan’s cases have been concentrated in the southeast. On July 9, officials said infections had been confirmed in 40 counties, with Monroe County reporting the most, at 215 cases. The state typically sees about 50 cases of cyclosporiasis a year.
The federal count is substantially different because it uses separate categories and does not update at the same pace. The Centers for Disease Control and Prevention reported 843 confirmed cases and 1,500 suspected cases across 31 states on Friday. Its tally included 86 hospitalizations and no deaths. The CDC expects the federal number to increase as delayed reports and investigations are processed.
Those figures should not be treated as competing measurements of exactly the same group of patients. Michigan’s count includes state reports gathered during an active investigation, while the CDC separates confirmed from suspected cases and receives information from jurisdictions at different times.
What cyclosporiasis does
Cyclosporiasis is caused by the parasite Cyclospora cayetanensis. Common symptoms include frequent watery diarrhea, loss of appetite, bloating, nausea and fatigue. Some patients also develop weight loss, body aches, headaches or vomiting.
The illness has an incubation period of about two weeks, meaning symptoms may not appear until roughly 14 days after exposure. That delay makes it difficult for patients to remember the foods they ate, particularly when an investigation begins weeks after the first illnesses.
Cyclospora infections generally occur when someone swallows food or water contaminated with the parasite. The organism’s environmental life cycle is one reason investigators focus on produce handling, food preparation and supply chains rather than assuming that every infection came from direct contact with another sick person.
Anyone with persistent watery diarrhea or unexplained weight loss should contact a health professional. Diagnosis may require specific stool testing, and telling a clinician about possible food exposures can help connect individual cases to a wider investigation.
Officials’ advice on produce
Michigan health officials are urging restaurants and commercial kitchens in southeastern Michigan to thoroughly wash leafy greens, snow peas, some herbs and raspberries, or to cook them when possible.
For lettuce, the department is recommending that consumers buy whole heads rather than pre-washed, bagged greens, remove and discard the outer leaves, and thoroughly wash the inner leaves. Those steps are precautions while the inquiry continues; they do not establish that every lettuce product is contaminated or that washing eliminates all risk.
Officials have not named a particular lettuce variety, salad kit, restaurant, retailer, grower or supplier. Investigators could still identify another food source as interviews, laboratory results and supply-chain records are reviewed.
Why tracing the outbreak is difficult
Epidemiologists investigating foodborne illness typically interview people with laboratory-confirmed infections about where they ate and shopped. They look for common exposures, such as the same restaurant, grocery store or ingredient, and then compare those reports with laboratory and distribution data.
In this outbreak, a typical six-week gap may exist between the beginning of illness and the arrival of a case report. Interviews often occur two to four weeks after infection, when patients may no longer recall every salad, garnish or meal they consumed. The parasite’s two-week incubation period adds another layer of uncertainty.
Barbara Kowalcyk, an associate professor at George Washington University’s Milken Institute of Public Health and director of its Institute for Food Safety and Nutrition Security, compared the process to assembling a puzzle. She said that when public-health capacity is reduced, investigators have fewer pieces with which to see the whole picture.
Kowalcyk said staffing shortages could mean some patients are interviewed six to eight weeks after becoming ill, rather than sooner. Michigan’s chief medical executive, Dr Natasha Bagdasarian, nevertheless said: “There is clearly a linked outbreak happening right now.”
The dispute over public-health capacity
The outbreak is unfolding after major changes to federal public-health funding and foodborne-illness surveillance. In March 2025, the Trump administration cut $11.4 billion in grants to state and local health departments. Although those grants were designated for pandemic activities, Kowalcyk said they also helped build local capacity for other emergencies.
Michigan public-health laboratories lost $5.5 million, according to Bridge Michigan. Kowalcyk said workers in state and local health departments can be supported by three or four different funding streams, so removing one may force agencies to reduce staff or move employees to part-time work. That can limit the ability to expand investigations quickly.
In July 2025, the administration also narrowed the scope of FoodNet, a program that actively monitored foodborne outbreaks and coordinated information across states. Its previous remit covered eight foodborne pathogens, including Cyclospora; the revised program focuses on shiga toxin-producing E. coli and salmonella.
FoodNet helped produce the widely cited estimate that 48 million people in the United States become ill from foodborne diseases each year, 128,000 are hospitalized and 3,000 die. Public-health consultant Gail Hansen warned in August 2025 that states lack the ability to coordinate information and data across state lines as effectively without the program’s broader role.
The administration has defended the change as a reduction in duplicative work, saying foodborne-pathogen investigations were not affected. A CDC update said the surveillance landscape has changed since FoodNet began in 1995 and that other systems now monitor infections involving FoodNet pathogens.
HHS senior press secretary Emily Hilliard said the Food and Drug Administration is investigating Cyclospora outbreaks with established epidemiological, laboratory and traceback tools in coordination with the CDC and state and local partners. She said the FDA has the personnel and resources needed to investigate and take regulatory action when warranted. Hilliard also said Cyclospora tracking “never stopped” and that the CDC is working with 3,000 health departments to collect data.
What happens next
Investigators will need to determine whether people in different counties consumed the same lettuce or greens, whether those products passed through a common distributor and whether laboratory evidence supports the suspected link. A confirmed grower or supplier could lead to a targeted public-health alert or regulatory action.
For now, the central message is narrower than avoiding all fresh produce: officials have identified leafy greens as a potential source, but have not confirmed a particular product. The case count is also likely to keep changing as delayed reports are confirmed, suspected infections are classified and investigators complete interviews.