A fast-growing cyclosporiasis outbreak has spread across at least 18 U.S. states, with federal and state health officials now tracking more than 400 confirmed cases as of early July 2026 a sharp jump from the 145 cases the CDC had officially logged just weeks earlier. The surge is being driven largely by an unusual cluster in Michigan, where more than 300 cases have been reported since June 22 alone, compared to the roughly 50 cases the state typically sees in an entire year. Health officials describe the illness’s hallmark symptom bluntly: “explosive,” watery diarrhea that can last for weeks if untreated.
Cyclosporiasis is caused by a microscopic parasite called Cyclospora cayetanensis, typically spread through raw produce or water contaminated with human feces. The CDC’s official surveillance count 145 domestically acquired cases across 17 states between May 1 and June 16, 2026 is already considered an undercount, since many people recover without seeking medical care or being tested.
Cyclosporiasis 2026 Key Dates
| Date | Development | Details |
|---|---|---|
| May 1, 2026 | Official start of the 2026 cyclosporiasis season | CDC considers May 1–Aug 31 peak season for U.S. cases |
| May 1 – June 16, 2026 | CDC surveillance window for the primary case count | 145 domestically acquired cases confirmed across 17 states |
| June 15–16, 2026 | CDC case snapshot published | 20 hospitalizations, 0 deaths reported; median age 42 |
| June 22, 2026 | Sudden spike begins in Michigan | Cases jump from a handful to over 150 within days |
| Late June 2026 | Michigan case count continues climbing | Reported cases in 7 counties surpass 300 |
| July 1, 2026 | CDC publishes updated surveillance map | Confirms no single common source identified yet; investigation ongoing |
| July 3–4, 2026 | National media coverage intensifies | Combined national total (CDC + Michigan) exceeds 400 cases across 18 states |
| Ongoing (July 2026) | FDA and CDC traceback investigation | Multiple in-state and multistate clusters under active review |
Which States Have Reported Cyclosporiasis Cases?
According to CDC and state health department data, confirmed cyclosporiasis cases in 2026 have been reported across a wide geographic spread, including Alaska, Louisiana, Texas, Colorado, Georgia, Florida, North Carolina, Virginia, Tennessee, Illinois, Wisconsin, Ohio, Pennsylvania, New York, New Jersey, Connecticut, and Massachusetts, with Michigan added as a major, rapidly escalating cluster in late June. Officials say New York, Illinois, and Texas have reported the highest case counts within the CDC’s original 17-state tally, while Michigan’s outbreak concentrated in Monroe, Lenawee, Washtenaw, Wayne, Livingston, Shiawassee, and Jackson counties has emerged as the fastest-growing and most closely watched cluster this summer. Health officials stress this is not confirmed as one single, connected multistate outbreak; rather, it’s a combination of a rising baseline case count and several distinct clusters being investigated separately.
What Causes Cyclosporiasis?
Cyclospora cayetanensis is a one-celled parasite that spreads through the fecal-oral route, most commonly by contaminating fresh produce or water during growing, washing, or handling. Foods historically linked to past U.S. cyclosporiasis outbreaks include raspberries, basil, snow peas, mesclun lettuce, cilantro, spinach, and other berries — meaning the parasite typically enters the food supply well before it reaches a grocery store shelf or restaurant kitchen, often through imported produce, though 2026 has seen a notably higher share of domestically acquired, non-travel-related cases compared to past years.
Cyclosporiasis Symptoms to Watch For
Health officials describe the defining symptom of cyclosporiasis as sudden, watery, and sometimes explosive diarrhea. The fuller symptom list includes:
- Watery diarrhea (often frequent and severe)
- Stomach cramping and bloating
- Nausea and vomiting
- Low-grade fever
- Fatigue
- Loss of appetite and weight loss in prolonged cases
Symptoms typically begin about a week after exposure, though the incubation period can range from two days to two weeks. Some infected people experience no symptoms at all, while others — particularly those who are immunocompromised, such as cancer patients or organ transplant recipients may face more severe or prolonged illness. Left untreated, cyclosporiasis can cause symptoms lasting anywhere from several days to several weeks, with occasional relapses even after apparent recovery.
How Cyclosporiasis Is Diagnosed and Treated?
Diagnosis requires a stool test ordered by a healthcare provider, since cyclosporiasis symptoms overlap with many other gastrointestinal illnesses and can’t be distinguished by symptoms alone. Once confirmed, the standard treatment is a course of the oral antibiotic trimethoprim-sulfamethoxazole (TMP-SMX) sold under brand names including Bactrim, Septra, and Cotrim — typically taken for 10 days. Most people with healthy immune systems recover fully, either with treatment or, in milder cases, on their own over time. People with penicillin or sulfa allergies should discuss alternative treatment options with their provider, since TMP-SMX is a sulfa-based medication.
Who’s at Higher Risk?
While most healthy adults recover without complications, certain groups face a higher risk of severe or prolonged illness:
- People who are immunocompromised, including those undergoing cancer treatment or living with a transplanted organ
- Older adults, given the median age of confirmed 2026 cases is 42, with cases ranging up to 86
- Anyone with chronic gastrointestinal conditions that could complicate diagnosis or recovery
- Households where fresh produce is consumed raw and unwashed, particularly leafy greens, herbs, and berries
Why This Outbreak Is Drawing Extra Scrutiny
Beyond the raw case numbers, this year’s outbreak has drawn attention for a second reason: it’s unfolding at a time when the CDC’s outbreak-response capacity has been affected by broader federal workforce and funding reductions. Public health reporting has noted that cuts to CDC staffing and pass-through funding for state and local health departments have raised concerns about the speed and thoroughness of the response, even as investigators from the CDC and FDA continue working to trace the source or sources behind the current clusters. HHS officials have defended the broader restructuring as an effort to reduce what they’ve described as bureaucratic inefficiency, while some former officials and researchers have warned that reduced capacity could slow detection and containment in future outbreaks.
How to Protect Yourself
Since there’s currently no vaccine for cyclosporiasis and no single confirmed contaminated product driving the 2026 outbreak, prevention centers on food handling practices:
- Wash all fresh produce thoroughly under running water, even if you plan to peel it.
- Scrub firm produce like melons and cucumbers with a clean brush before cutting.
- Cut away bruised or damaged sections of fruits and vegetables before eating.
- Refrigerate pre-cut or pre-prepared produce promptly rather than leaving it at room temperature.
- Seek medical care promptly if you experience sudden, watery diarrhea lasting more than a day or two, especially if you live in one of the affected states.
The 2026 cyclosporiasis outbreak has grown well beyond the CDC’s initial 145-case count, with Michigan’s rapid cluster pushing the real national total above 400 cases across 18 states. While the illness is treatable and rarely life-threatening for healthy adults, the scale and geographic spread of this year’s cases combined with an ongoing, unresolved source investigation — has made it one of the more closely watched foodborne illness stories of the summer. Anyone experiencing persistent watery diarrhea, especially in an affected state, should contact a healthcare provider for testing rather than waiting it out, both for their own recovery and to help investigators identify the outbreak’s source.
