A parasitic stomach bug, cyclosporiasis, has sickened thousands across the United States, prompting public health officials to investigate potential sources while consumers navigate what foods are safe to eat. As of the latest reports, confirmed infections have surpassed 5,800, with thousands more cases under review.
Michigan has been particularly affected, reporting over 4,300 cases, a sharp increase from its typical yearly average of fewer than 50. The outbreak has led to 102 hospitalizations in the state.
Cyclosporiasis is caused by the Cyclospora parasite, which is transmitted through contaminated food and is not considered contagious from person to person. The parasite adheres to fresh produce and is difficult to eliminate. Symptoms typically emerge two days to two weeks after exposure and include prolonged watery diarrhea, stomach cramps, nausea, fatigue, loss of appetite, and weight loss. While treatable with antibiotics, the illness can last for weeks if left untreated and may cause dehydration. Approximately one in 11 cases has required hospitalization, though no deaths have been reported.
"Foodborne illnesses like Cyclospora wreak havoc on the gastrointestinal tract, causing large microbiome imbalances that can mean long-lasting GI symptoms," said Dr. Mark Pimentel, a gastroenterologist at Cedars-Sinai Hospital.
Potential Sources and High-Risk Foods
Investigators are focusing on lettuce and leafy greens as potential culprits, as case interviews in Michigan frequently mention lettuce. The parasite spreads via the fecal-oral route, often contaminating produce at the farm level through infected human feces. Unlike other foodborne pathogens, Cyclospora originates from humans, its only natural host.
Jason Reese, a food safety expert, noted that contamination often occurs on the farm and that the parasite is undetectable on produce in stores or restaurants, lacking any smell or visible signs.
Certain types of produce are considered riskier due to their physical characteristics. Bagged salads and salad kits are at the top of the list of foods to avoid. "The riskiest items are bagged salads and kits, herbs like cilantro and basil, green onions, snow peas, leafy greens and raspberries," Reese stated. Bagged produce carries an extra risk because the processing and packaging can create more contamination opportunities, and the "pre-washed" label does not guarantee safety during an active outbreak.
Fresh herbs, particularly cilantro and basil, are also high-risk because their delicate leaves are difficult to wash thoroughly and they are often consumed raw. Produce with textured surfaces, such as raspberries and blackberries, can trap the parasite's oocysts in their crevices, making them exceptionally hard to remove. Green onions and snow peas have also been flagged as items of concern.
Safer Produce Choices and Prevention Methods
Health officials and experts emphasize that consumers do not need to eliminate produce entirely but should make informed choices. Whole heads of lettuce are a safer alternative to bagged mixes. The recommendation is to "buy whole heads of lettuce, discard the outer layers and thoroughly wash what's left." Reese advised that for raw produce consumption, consumers should "always choose whole heads of lettuce instead of the pre-washed bagged options and throw out two to three layers of the outer leaves before thoroughly washing all inner leaves under running water."
Frozen and canned fruits and vegetables are considered safe alternatives, as the processing involved, such as blanching and freezing, effectively eliminates the parasite. Cooked vegetables are the safest option, as the Cyclospora parasite is killed by heat at 158 degrees Fahrenheit.
Produce with a peel, like bananas, avocados, oranges, melons, cucumbers, and pineapples, offers a natural barrier; the exterior should be washed before cutting. Peeled items such as carrots, potatoes, and apples are also safer, as peeling removes the contaminated surface layer.
While thorough washing is essential, it may not completely remove the parasite. "People should thoroughly wash fresh fruits and vegetables under water before eating, even if their produce looks clean," said Dr. Alan Bulbin, director of infectious disease at Catholic Health’s St. Francis Hospital. For herbs, Reese recommended separating leaves and washing them under running water. Snow peas and green onions require washing and surface rubbing, while melons and cucumbers should be scrubbed with a produce brush and running water.
Experts stress using running water for washing, not a basin, to avoid recontamination. They also advise against using vinegar, baking soda, saltwater, or lemon juice for washing, as plain tap water is proven to be most effective. Soaps and bleach are not recommended as they can be absorbed by produce. Vigilance against cross-contamination is crucial, including using clean cutting boards and utensils. Unwashed produce should be kept separate from ready-to-eat foods and raw meats, poultry, or seafood. Hand washing and sanitizing in the kitchen are also emphasized as critical prevention measures.