A family sits down for taco night, piles on some shredded lettuce from a bag in the fridge, and thinks nothing more of it. Weeks later, one of them is doubled over with diarrhea so severe and sudden that doctors have started calling it, bluntly, “explosive.” That’s the pattern playing out across several US states right now, and health officials say it’s already the worst year on record for this particular parasite.
What’s Happening
Cases of cyclosporiasis — an intestinal illness caused by the parasite Cyclospora cayetanensis — have surged past the previous US record of about 4,700, set in 2019, with more than 30 states reporting infections so far this year. Michigan alone has logged over 3,300 cases, and federal officials say outbreaks in Michigan, Ohio, Kentucky, and West Virginia appear to be linked. Michigan typically sees only 40 to 50 cases a year; this year’s total in that state alone is more than 50 times the norm.
Key Takeaways
- Cyclosporiasis cases in the US have already surpassed the 2019 record, with Michigan reporting over 50 times its typical annual case count.
- Michigan health officials say lettuce and salad greens are a likely source, based on more than 1,000 patient interviews, though no specific grower or product has been confirmed.
- The parasite causes watery, sometimes explosive diarrhea and is spread through food or water contaminated by feces — not person-to-person contact.
- Buying whole heads of lettuce instead of bagged or pre-mixed salad, and discarding the outer leaves, are the current recommended precautions.
- This is one of many foodborne parasites tracked globally — a separate WHO report estimates they cause nearly 5 million years of healthy life lost worldwide each year.
Why Lettuce Keeps Showing Up in These Outbreaks
Michigan’s investigation, based on interviews with more than 1,000 sick patients, keeps turning up lettuce as a common thread — though officials are careful to say no specific type, grower, or supplier has been confirmed, and other foods haven’t been ruled out. Bagged and pre-washed salads are a frequent culprit in outbreaks like this one, partly because they’re eaten raw and partly because there are multiple points in the supply chain — growing, washing, bagging, distribution — where contamination can slip in. “Washed and ready to eat” on the label doesn’t mean pathogen-free; health officials still recommend washing it yourself. Past North American Cyclospora outbreaks have also been traced to fresh basil, cilantro, raspberries, snow peas, and green onions, so the caution extends a bit beyond just lettuce.
What to Actually Do About It
Current health department guidance is fairly simple: buy whole heads of lettuce rather than bagged salad or pre-mixed kits, discard the outer two or three leaves before use, and wash produce thoroughly under running water. Cooking kills the parasite entirely, so the risk is specific to things eaten raw. If you or someone in your household develops sudden, watery, or unusually frequent diarrhea after eating salad or fresh greens in an affected area in the past few weeks, it’s worth telling your doctor and specifically requesting a Cyclospora test — standard stool tests don’t always catch it, since the parasite doesn’t shed consistently.
The Bigger Picture
Cyclospora is one of many parasites that spread through food, and a separate report from the World Health Organization, published in The Lancet, estimated that foodborne parasites caused nearly 4.9 million years of healthy life lost globally in 2021. The pork tapeworm carried the largest health burden of any parasite measured, followed by a liver fluke common in parts of Asia, and Toxoplasma gondii, best known for its link to cat litter. None of that changes what to do about the current outbreak, but it’s a reminder that thorough washing, proper cooking, and basic hygiene around food handling matter well beyond just this one outbreak.
Sources: Michigan Department of Health and Human Services, outbreak updates (July 2026); Lake, R.J. et al. (2026). Global burden of foodborne parasitic diseases, 2021. The Lancet.