Michigan normally records around 50 cyclosporiasis cases in an entire year. By mid-July 2026, the state had logged more than 3,300. That gap alone signals something has gone badly wrong in the food supply, and the culprit appears to be something most Americans eat without a second thought.
State officials announced this week that an outbreak of cyclosporiasis that has sickened more than 2,600 Michigan residents is believed to have originated with infected lettuce or salad greens. The illness is spreading fast and far beyond Michigan’s borders. As of July 10, 31 states have reported cases to the U.S. Centers for Disease Control and Prevention. A surge of cases of the intestinal illness that causes diarrhea and nausea has been detected across those states, though the source is still under investigation.
The scale of this outbreak is unlike anything Michigan has seen before. The state usually reports only around 50 cases of cyclosporiasis each year, making the current outbreak unusually large. The Associated Press reported it is the largest outbreak of its kind in Michigan’s history and one of the country’s largest in years. Nationally, the numbers are still climbing, with cases surpassing 4,000 across 31 states, Michigan representing by far the largest cluster.
One fast-food chain has also become entangled in the investigation. Federal and state health officials are reportedly looking into Taco Bell after Detroit-area Taco Bell restaurants posted signs they were “currently unable to sell Lettuce, Cilantro Onion, Pico de Gallo, and Guacamole due to a nationwide recall.” In a statement, Taco Bell said: “The health and safety of our guests is our top priority. Public health officials have not confirmed a link to Taco Bell or any specific ingredient, supplier, restaurant or retailer. While authorities continue their broader review, Taco Bell has voluntarily and temporarily removed limited ingredients at select restaurants as a precautionary measure. We will continue to closely monitor the situation and follow the guidance of public health authorities.”
What Is Cyclosporiasis and How Does It Spread?
Cyclospora is a parasite that causes frequent, watery diarrhea, as well as nausea and stomach cramps. It is contracted by eating or drinking something contaminated with the parasite. More precisely, Cyclospora is generally transmitted when infected feces contaminate food or water. On a farm, that can happen through irrigation water drawn from a contaminated source, or through inadequate sanitation among workers who handle fresh produce.
Direct person-to-person transmission is unlikely because the Cyclospora parasite needs time, days to weeks, after being passed in a bowel movement before it becomes infectious for another person. That biological quirk is part of what makes outbreaks so hard to trace. By the time someone feels sick, the contaminated meal that caused it was eaten up to two weeks prior. As CNN reported, cyclosporiasis cases are slow to be counted and may require patients to recall what they ate weeks ago; genomic testing for cases is complicated; and some public health systems that track foodborne illness have recently faced sharp cuts.
The parasite itself is microscopic, formally known as Cyclospora cayetanensis. It is a single-celled, spherical parasite, too small to see without a microscope, first described in humans in 1994.
The Symptoms – and Why They’re Easy to Dismiss
Cyclospora causes watery, sometimes explosive diarrhea that can wax and wane for weeks, along with cramping, gas, nausea, fatigue, and loss of appetite. That symptom pattern – diarrhea that comes and goes rather than resolving steadily – is one of the clearest signals that distinguishes this illness from a 24-hour stomach bug. Illnesses from the parasite are assumed to be an undercount since many people who get cyclosporiasis may be embarrassed to see a doctor or may try to wait out their symptoms at home.
People become ill by eating or drinking something that’s been contaminated several weeks prior, usually fresh produce or water from a swimming pool, though Michigan health officials at the MDHHS said there is “currently no evidence linking recreational water activities to this outbreak.”
People at higher risk of severe illness or dehydration, including older adults, young children, organ transplant recipients, and people undergoing chemotherapy, are encouraged to take extra precautions. Dehydration is the main clinical concern and can land people in the hospital. As of July 9, 2026, Michigan alone had reported 44 hospitalized cases. No deaths have been reported in the outbreak.
Without treatment, the illness tends to drag on. The parasite needs time outside the body to become infectious again, which is why direct person-to-person spread doesn’t happen, but inside a single host, the infection can persist for weeks. Symptoms can appear to ease and then return, cycling through periods of feeling almost normal before another wave hits. This relapsing pattern is one reason doctors who don’t immediately recognize the parasite may dismiss or misattribute the illness.
Why Washing Your Produce Won’t Protect You During a Cyclosporiasis Outbreak
The parasite produces protective egg-like structures called oocysts that cling to produce surfaces and are resistant to chlorine disinfection at concentrations used in municipal water systems and commercial produce washing. In plain terms: the standard produce-safety measures that work against bacteria like E. coli or Salmonella simply don’t work here.
Chlorine and other common antimicrobial chemical treatments are not effective against C. cayetanensis. As a parasite, C. cayetanensis behaves differently than other gastrointestinal pathogens that commonly cause foodborne illness.
Michigan health officials at the MDHHS have stated explicitly that “pre-washed” packaging does not guarantee safety and that rewashing bagged lettuce is unlikely to remove the parasite. That means the salad kit labeled “triple-washed” in your refrigerator offers no meaningful protection if the leaves were contaminated before packing. Freezing also does not kill Cyclospora oocysts.
The only reliable way to destroy the parasite is heat. Cooking food to at least 158°F (70°C) kills it. Raw salads and uncooked greens offer no protection during an active outbreak, which is precisely why the implicated foods pose such a challenge.
How the Investigation Works – and Why It Takes So Long
As Dr. Natasha Bagdasarian, Michigan’s Chief Medical Executive, said in a statement, “Produce may have been grown on the other side of the country, possibly even in other countries, then processed somewhere else before coming into Michigan.” The supply chain complexity makes tracing a single contaminated batch extraordinarily difficult.
People who agree to be interviewed are asked to remember what they ate weeks earlier, which is difficult and unreliable. In addition to interviews, investigators also look at people’s digital and paper trail, including restaurant and grocery receipts. State health officials said they have completed more than 1,000 interviews with infected individuals while working with local, state, and federal partners to trace the source of the outbreak.
Dr. Bagdasarian said: “Although we do not have a definite product identified as the source of the outbreak, we want to let Michiganders know what we have learned so far so they can take steps to protect their families. Early information has shown lettuce as a common product that regularly comes up during the investigation.”
CNN reported that the U.S. Department of Health and Human Services says cyclosporiasis cases are expected to rise over the summer months, and the agency is working with federal and state partners to monitor case counts and cluster activity.
Past U.S. cyclosporiasis outbreaks have consistently been associated with fresh, imported produce. A 2018 report published in the CDC’s Morbidity and Mortality Weekly Report found that past outbreaks have been associated with various types of imported fresh produce, including basil, cilantro, and raspberries. The 2026 outbreak fits that historical pattern, even though the specific source has not yet been confirmed.
Diagnosis and Treatment
Standard stool culture panels check for Salmonella, E. coli, Shigella, and Campylobacter. Cyclospora is not on these panels. As CDC clinical guidance makes clear, testing for Cyclospora is not routinely conducted in most U.S. laboratories, and healthcare providers must specifically request it. Detecting the parasite requires a separately ordered modified acid-fast stain or a Cyclospora-specific PCR, according to Medical Daily’s coverage of the CDC’s clinical alert. If a doctor runs a “standard” stool culture, they may find nothing at all – even if cyclosporiasis is the cause.
Asking your doctor specifically about the ongoing outbreak and requesting a test for Cyclospora cayetanensis by name gives you the best chance of a prompt diagnosis if your symptoms persist. Treatment is seven to ten days of the combination antibiotic sulfamethoxazole-trimethoprim, sold as Bactrim or Septra. Without that treatment, the illness can last weeks. Symptoms that seem to improve and then return are a known feature of this infection, not a sign that the illness is resolving on its own, and they often lead people to delay seeking care longer than necessary.
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What to Do Now
The most practical step right now is to avoid bagged, pre-washed lettuce and pre-mixed salad kits until the outbreak source is confirmed. Michigan’s MDHHS recommends purchasing whole heads of lettuce rather than pre-washed, bagged lettuce or pre-mixed salad kits, and removing and discarding the outer two to three layers of leaves before preparation. This won’t eliminate risk entirely, but it reduces the surface area of the leaf most exposed during field or transport contamination.
When possible, greens should be cooked to at least 158°F (70°C), which kills the parasite. Sautéed or wilted greens – spinach in a stir-fry, kale in a soup – pose far less risk than a raw salad during an active outbreak. If you have symptoms that match this illness, particularly watery diarrhea that seems to improve and then returns, don’t wait it out. The CDC’s cyclosporiasis surveillance page urges people with symptoms to seek medical care, and specifically notes that the parasite requires a targeted lab test to detect. The combination antibiotic treatment works well when started promptly – the problem is getting diagnosed in the first place.
Disclaimer: This information is not intended to be a substitute for professional medical advice, diagnosis, or treatment and is for information only. Always seek the advice of your physician or another qualified health provider with any questions about your medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice or treatment because of something you have read here.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.