Federal public health officials are investigating a multistate Cyclospora outbreak that has sickened at least 145 people in 17 states since May 1, 2026. The source of the contamination has not yet been identified, and summer — now underway — is the peak season for this intestinal parasite in the United States.
According to the CDC, local, state, and federal public health authorities are investigating several clusters of cases, with illness onset dates ranging from May 1 through June 7, 2026. Three people have been hospitalized. No deaths have been reported.
Past outbreaks of Cyclospora in the United States have repeatedly been linked to fresh produce — particularly leafy greens, cilantro, basil, and imported fresh herbs. Investigators have not yet identified a specific food or supplier in the current outbreak.
Why This Matters
Cyclospora cayetanensis is a microscopic waterborne parasite that causes a prolonged intestinal illness called cyclosporiasis. Unlike many foodborne pathogens that cause illness within hours of exposure, Cyclospora has an incubation period of about one week. Illness typically lasts weeks if untreated — and in some cases can stretch to months in immunocompromised individuals.
Because it is not part of routine stool testing panels, Cyclospora is frequently missed by physicians who do not specifically request it. This means both cases and outbreaks are likely underdetected — a challenge that has hampered traceback efforts in recent years as well.
What We Know So Far
The CDC's Cyclospora surveillance page shows that as of June 16, 2026, 145 domestically acquired cases have been confirmed, with a median age of 43 and 62 percent of patients being female. Three people have been hospitalized. The median illness onset date was May 19, 2026.
An additional 45 travel-associated cases have been reported in people who were outside the United States during their exposure window.
The FDA's outbreak investigations table lists Cyclospora investigation reference 1375 as active as of the most recent update. The case count has grown, and the traceback investigation has not yet identified a specific implicated food product.
Past U.S. outbreaks have been linked to bagged salad kits, fresh cilantro from Mexican farms, fresh basil, mixed leafy greens, arugula, and baby spinach. The pattern in the current outbreak is consistent with those food categories — but investigators have been unable to confirm a specific product or distribution chain.
Where the Risk Is Highest
Based on the CDC's case map, cases in the current outbreak span 17 states. Historically, Cyclospora outbreaks have clustered around states in the South, Midwest, and East Coast — areas with high consumption of imported fresh produce.
The CDC and FDA have noted that the true number of cases is likely higher than what is reported, because some people recover without medical care and are never tested for the parasite specifically.
Past outbreaks have involved restaurant chains with nationwide distribution networks — underscoring how a single contaminated producer supplying multiple chains can spread illness across dozens of states before investigators identify the source.
What Doctors and Experts Say
Public health experts note that Cyclospora is particularly challenging to identify because its spores must incubate for seven to 14 days in the environment before becoming infectious. This means contamination on produce may have occurred significantly earlier than when illness appears in patients — a gap that complicates traceback.
According to a Food Safety Magazine analysis of recent Cyclospora outbreaks, none of the major epidemiological studies for outbreaks in 2023 and 2024 — which together involved more than 3,000 cases — was able to definitively identify the mode or method of disease transmission. "These processes remain an unresolved mystery," the analysis states.
Physicians are advised to specifically request Cyclospora testing when patients present with prolonged watery diarrhea in the summer months, particularly with a history of leafy green consumption.
What the Evidence Shows — and What It Does Not
Cyclospora is a nationally notifiable disease, which means states are required to report cases to the CDC. However, reporting is voluntary in Pennsylvania, which may undercount the true national burden.
The current active investigation has not confirmed a food product or supplier. Until a specific recall is issued or a specific product is implicated, there is no public guidance to avoid a particular food item. The FDA and CDC advise maintaining standard produce hygiene practices.
Who Faces the Greatest Risk?
People most vulnerable to severe or prolonged Cyclospora illness include:
- Immunocompromised individuals, including those living with HIV, organ transplant recipients, or people on immunosuppressive medications
- Adults between 25 and 65 who consume fresh leafy greens, herbs, and salads regularly
- Travelers returning from regions where Cyclospora is endemic, including parts of Latin America, South and Southeast Asia, and the Caribbean
- Elderly adults and those with underlying digestive conditions
Children and adults who consume large quantities of fresh produce — particularly in summer — face a meaningful, if still relatively low, risk of exposure until the source is identified.
Symptoms and Warning Signs to Watch For
Cyclospora causes a gastrointestinal illness that differs from typical food poisoning in its timing and persistence. Symptoms typically appear about seven days after exposure and may include:
- Watery diarrhea, often frequent and explosive
- Fatigue and weakness
- Loss of appetite and weight loss
- Nausea and bloating
- Low-grade fever and muscle aches
- Stomach cramps
The illness can last from a few weeks to several months if untreated. Symptoms may appear to improve and then return. If you experience prolonged diarrhea lasting more than three days, especially after eating fresh produce or returning from travel, contact your health care provider and specifically mention Cyclospora as a diagnostic consideration.
What You Can Do Now
- Wash all fresh produce — including pre-washed or bagged salad greens — under cold running water before eating. Note that Cyclospora is not reliably removed by washing, but washing is still the recommended standard practice.
- If you develop prolonged watery diarrhea lasting more than three to five days, especially during summer, tell your doctor to specifically test for Cyclospora. Standard stool cultures often miss this parasite.
- If diagnosed, Cyclospora is treated with trimethoprim-sulfamethoxazole (TMP-SMX), also known as Bactrim. This is the only validated treatment. Do not attempt to treat with over-the-counter antidiarrheal medications as a substitute — they address symptoms but not the infection.
- Monitor the FDA's outbreak investigations page for updates if a specific food product or recall is identified.
- People who are immunocompromised should discuss their fresh produce consumption with their health care provider during active summer outbreak seasons.
Cost and Access: What Patients Should Know
Cyclospora testing requires a specific laboratory request — it is not part of a standard stool culture panel ordered for acute diarrhea. Patients who believe they may have been exposed should explicitly ask their clinician to include Cyclospora in any stool testing. The test is generally covered by health insurance when ordered by a physician.
Treatment with TMP-SMX is inexpensive in generic form and widely available.
What Happens Next
The FDA and CDC are continuing to investigate. An implicated food product may be publicly identified in the coming weeks, at which point a public health advisory or product recall may follow. The Cyclospora outbreak season runs May 1 through August 31. MedicalDaily will report on any new recalls or food safety advisories as they are announced.
The Bottom Line
An active Cyclospora investigation is underway, with 145 confirmed cases in 17 states and no source yet identified. Summer is peak season for this parasite. Until investigators find the contaminated food item, Americans should maintain vigilant produce hygiene and — if they develop prolonged summer diarrhea with fatigue — specifically ask for Cyclospora testing. Early treatment with the correct antibiotic shortens illness duration significantly.
