Officials point to lettuce and salad greens, but no supplier has been confirmed
Michigan health officials have pointed to lettuce and salad greens as a potential source of a fast-growing cyclosporiasis outbreak, but warned that the investigation is not over.
The Michigan parasite outbreak has already led to thousands of reported illnesses, with state officials saying early findings suggest raw leafy produce may be involved. No specific type of produce, grower or supplier has been confirmed, and health authorities have cautioned that other food sources have not been ruled out.
Cyclosporiasis is caused by the Cyclospora parasite. It can trigger watery diarrhoea, loss of appetite, weight loss, stomach cramps, nausea and fatigue. The illness can be especially hard to trace because symptoms may take up to two weeks to appear, leaving patients struggling to remember exactly what they ate.
Michigan has been hit hardest. State health officials have reported 2,640 cases, while Ohio has reported 177. The CDC has separately listed 843 confirmed cases and 1,500 suspected cases across 31 states, with 86 hospitalisations and no deaths reported.
The Michigan parasite outbreak has now prompted new advice for restaurants and commercial kitchens in the south-east of the state. Officials are urging food handlers to wash leafy greens, snow peas, some herbs and raspberries thoroughly. When possible, they say cooking produce is the safest option.
After lettuce and salad greens emerged as a potential source, Michigan officials also advised buying whole heads of lettuce instead of pre-washed bagged greens. They recommended removing the outer leaves and washing the inner leaves under running water.
The warning does not mean every salad is unsafe. But it does show how difficult foodborne illness investigations can become when fresh produce is involved. Epidemiologists must interview people with lab-confirmed infections and look for shared meals, restaurants, shops or ingredients. Those conversations often happen weeks after the person became ill.
The Michigan parasite outbreak is also unfolding amid renewed debate about public health funding. The report notes that the Trump administration previously cut grants to state and local health departments and narrowed the scope of FoodNet, a programme used to monitor foodborne illness. Critics argue those changes make it harder to build a full picture during outbreaks.
Barbara Kowalcyk, a food safety expert at George Washington University, compared outbreak investigations to assembling a puzzle. She said removing pieces makes it harder to see the whole picture, especially when local health teams are already stretched.
Federal officials have defended the system. The Department of Health and Human Services said the FDA is investigating Cyclospora outbreaks using established epidemiological, laboratory and traceback tools, working with the CDC and state and local partners. It also said Cyclospora tracking has not stopped.
For families and businesses, the immediate focus is prevention. People with sudden and ongoing diarrhoea are being urged to contact a health care provider for testing and treatment. Health officials say cyclosporiasis can be treated with antibiotics, rest and fluids.
The Michigan parasite outbreak has left investigators searching for a clear food link while consumers wait for firmer answers. Lettuce and salad greens may be the strongest lead, but the illness has not yet been traced to one farm, supplier or product.
Until they find the source, the Michigan parasite outbreak remains a public health test for consumers, restaurants and the agencies trying to track a parasite that can move quietly through the food supply before anyone knows it is there.