Michigan alone has reported more than 3,300 cases of a parasitic illness this summer – in a state that typically records around 50 cases in an entire year. That scale isn’t explained by a seasonal uptick. Something specific is driving it, and health officials across four states are racing to figure out what.
The culprit is Cyclospora cayetanensis, a microscopic single-celled parasite that causes a gastrointestinal illness called cyclosporiasis when people eat food or drink water contaminated with it. The illness does not spread directly from person to person, which makes a contaminated food source the only plausible explanation for an outbreak of this size.
Since May 1, 2026, the CDC has received reports of 1,645 confirmed domestic cases of cyclosporiasis and is aware of more than 5,100 additional cases requiring further analysis. That is substantially higher than the 249 cases reported nationally by the same point last year. State-level data suggests the national count has already surpassed the previous U.S. record of approximately 4,700 cases set in 2019. No deaths have been reported, but the scale of the outbreak and the speed at which it has grown prompted the CDC to issue a formal Health Alert Network notice to clinicians across the country.
How the Parasite Works
Symptoms of cyclosporiasis typically begin about one week after exposure, though onset can occur anywhere between two and fourteen days after being infected. By the time someone feels sick, they may not remember – or may have no way to know – exactly which meal was contaminated.
The most common symptoms are watery diarrhea (which can be frequent and explosive), loss of appetite, weight loss, bloating, nausea, and fatigue. Less common symptoms include low-grade fever and vomiting. The illness can feel like a severe stomach bug, but it behaves differently. Without treatment, symptoms can follow a relapsing-remitting pattern that lasts from a few days to a month or longer. People often feel slightly better, assume they’ve recovered, and then relapse – sometimes multiple times over several weeks.
Case counts rise during the spring and summer months, so the CDC considers May 1 through August 31 the annual cyclosporiasis season. There’s also a built-in delay before the parasite even becomes dangerous. According to the FDA, it takes at least one to two weeks in the environment for Cyclospora to become infectious after being passed in a bowel movement, which means person-to-person transmission is effectively ruled out. Someone would have to consume feces that had already been sitting in an environment for a week or more – in practice, that means contaminated irrigation water or feces that reached produce during growing or processing.
Where This Outbreak Is Hitting Hardest
The CDC believes that 400 of the confirmed cases – spread across Michigan, Ohio, West Virginia, and Kentucky – are connected as part of a large multistate outbreak, suggesting a common source. The agency is also investigating several additional large clusters in other states.
Michigan alone had reported 3,309 cyclosporiasis cases as of mid-July, according to NPR. Ohio is also seeing a significant rise, with nearly 400 cases reported in the state – well above its typical annual count of around 70. Dr. Gwen Biggerstaff, deputy director of the CDC’s Division of Foodborne, Waterborne, and Environmental Diseases, told reporters at a July 14 briefing that the 2026 numbers are “much, much higher than what we’ve seen last year or the year before” and called the pattern “a very big shift” from typical cyclosporiasis seasons.
Michigan’s Department of Health and Human Services has conducted more than 1,000 patient interviews as part of its investigation. Early information points to lettuce or salad greens as the most likely culprit, though other foods can’t be ruled out, and no specific type, grower, or supplier has been identified as the source. The diagnosis is also not included on all standard lab workups for stomach bugs and may require a special order from a doctor who suspects it – meaning by the time a person becomes a confirmed case and their data is reported to public health authorities, several weeks may have already passed since the actual exposure.
Previous U.S. outbreaks of cyclosporiasis have been associated with raspberries, basil, cilantro, snow peas, and lettuce, according to the FDA. The number of reported cases started rising about a decade ago, with a particularly notable spike in 2018 and 2019. In 2018, McDonald’s stopped selling salads at approximately 3,000 restaurants across 14 Midwest states after federal health officials linked them to hundreds of cyclosporiasis cases, according to a CDC report published in the MMWR.
Cyclosporiasis Prevention: Why Hand Sanitizer Won’t Save You
Alcohol-based hand sanitizers are nowhere near as effective against Cyclospora as soap and water. The same applies to produce. Chemical disinfectants and standard sanitizers are not effective against Cyclospora oocysts (the egg-like stage of the parasite’s life cycle), as the FDA notes. Spraying your salad greens with a vegetable wash or soaking them in diluted bleach won’t eliminate the risk.
What does work is physical removal under running water. Thoroughly washing fresh produce under clean running water before eating or cooking is a recommended frontline defense – and the emphasis on running water matters. Soaking produce in a bowl or sink allows any parasites dislodged from one item to potentially contaminate another. Running water physically washes organisms off and away.
For handwashing, the standard protocol is the most effective. Washing hands with warm water and soap for at least 20 seconds can help eliminate germs. This applies before and after handling raw produce, before eating, and after using the bathroom.
Heat is also reliable. The CDC’s July 14 briefing confirmed that heating food to at least 158°F (70°C) kills Cyclospora. For anyone in an affected region who is immunocompromised, elderly, or pregnant, that’s a meaningful consideration when deciding whether to eat raw salad greens right now.
Basil, cilantro, spinach, raspberries, snow peas, and mesclun-type lettuce blends have repeatedly been implicated in past outbreaks, particularly when imported during peak growing season. University of Delaware professor Kalmia Kniel told Newsweek that Cyclospora oocysts can attach to the hairlike projections on raspberries and cilantro, making physical removal difficult even with careful washing. While there is no recall in effect as of this writing and no specific product has been flagged, anyone eating raw leafy greens and salads – especially in Michigan, Ohio, West Virginia, and Kentucky – should be applying the most careful washing practices available. For high-risk individuals, briefly cooking or blanching those greens is a more reliable option than washing alone.
Read More: Riskiest and Often Recalled Foods
Getting Diagnosed Is Harder Than It Should Be
Routine stool cultures ordered for acute diarrhea will not detect Cyclospora. Even when people do the right thing and see a doctor promptly, the infection is routinely missed on standard lab panels. Confirming infection requires a specific modified acid-fast stain or a PCR assay that must be requested by name, according to the CDC’s clinical guidance.
Oocyst shedding can be intermittent, which means a single negative sample does not rule out infection, and repeat sampling may be warranted when clinical suspicion is high. If you’ve had prolonged watery diarrhea – especially a pattern where symptoms ease and then return – and you’ve eaten fresh produce recently, ask your doctor directly: “Does this stool test include Cyclospora?” That question can make the difference between weeks of unexplained illness and a prompt, correct diagnosis.
The CDC’s clinical overview notes that reported complications of untreated cyclosporiasis include malabsorption, cholecystitis (gallbladder inflammation), and reactive arthritis. These aren’t common outcomes, but they are real risks for people who go undiagnosed and untreated for an extended period.
The Treatment That Works
According to CDC clinical guidelines, the treatment of choice for cyclosporiasis is trimethoprim-sulfamethoxazole, commonly known as TMP-SMX and sold under the brand names Bactrim and Septra. The standard dosage for otherwise healthy adults is TMP 160 mg plus SMX 800 mg taken orally twice daily for seven to ten days. Most patients begin feeling better within several days of starting the medication.
Immunocompromised patients, including people living with HIV, may require a longer course of treatment. For patients with sulfonamide intolerance, the same CDC guidelines note that no highly effective alternative has been identified – ciprofloxacin has shown only modest activity in limited studies, and most other antibiotics have not demonstrated reliable efficacy against Cyclospora.
Left untreated, cyclosporiasis is rarely life-threatening but can be miserable and prolonged, with symptoms dragging on for weeks to over a month without appropriate therapy, and relapse is possible even after apparent recovery. This infection does not reliably resolve on its own in a reasonable timeframe. If you suspect cyclosporiasis and you’re in an affected region, the right move is to see a doctor and specifically request testing rather than waiting it out.
What to Do Right Now
The 2026 outbreak has no confirmed food recall attached to it yet. That absence doesn’t mean the food supply is safe – it means investigators haven’t locked down the source. In the meantime, the practical steps for cyclosporiasis prevention are concrete and doable.
Wash all fresh produce thoroughly under running water, not in standing water. Pay particular attention to leafy greens, herbs like cilantro and basil, and soft berries – categories with the longest history of Cyclospora contamination. If you or anyone in your household is immunocompromised, pregnant, or over 70, seriously consider cooking those items rather than eating them raw until the outbreak is resolved. No hand sanitizer will substitute for soap-and-water handwashing before and after handling food, and a full 20 seconds with warm water and soap is the actual standard – not a quick rinse.
Of the 1,645 confirmed cases reported to the CDC, 141 patients – about 9% – required hospitalization, and no deaths have been reported. Most people who get cyclosporiasis will recover without a hospital stay, but a significant minority won’t. If diarrhea has lasted more than a week, if symptoms keep returning after apparent improvement, or if you’re becoming dehydrated, don’t assume it’s a routine stomach virus. Get tested – and make sure the test actually looks for Cyclospora.
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.
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