If you have seen headlines this month about a fast-growing “diarrhea parasite” spreading across the United States (US), you are not alone. You are watching one of the more significant foodborne illness outbreaks in recent years. Cyclosporiasis, an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis, has surged well beyond a typical season, prompting a formal Health Alert Network notice from the CDC to clinicians and public health practitioners nationwide.
For hospitals, health departments, healthcare coalitions, and emergency management partners, this outbreak offers an important look at disease surveillance, multi-state coordination, and public health communication in action. Below is what we know so far—and why it matters.
What Is Cyclosporiasis?
To begin, cyclosporiasis is a gastrointestinal illness caused by the parasite, Cyclospora cayetanensis, a single-celled parasite typically transmitted through food or water contaminated with feces. Unlike many illnesses, such as norovirus, cyclosporiasis does not spread from person to person, according to Johns Hopkins Medicine Common symptoms include watery, sometimes prolonged diarrhea, along with loss of appetite, weight loss, nausea, and fatigue. In most cases, symptoms begin about one week after exposure, although they can develop anywhere from two to fourteen days later, according to CDC’s Health Alert Network notice.
A Season Unlike Recent Years
Typically, CDC designates May 1 through August 31 as the annual cyclosporiasis season, when case counts typically rise with warmer weather, according to CDC surveillance data. However, 2026 has been vastly different. Case counts have climbed far faster than in recent years.
As of July 14, 2026, CDC had confirmed 1,645 domestically acquired cases across 34 states, with more than 5,100 additional cases still under review, per the CDC Health Alert Network notice. By the same point in 2025, the national count stood at just 249 cases, more than a sixfold increase year over year.
Michigan has emerged as the epicenter of the outbreak. As of July 23, the Michigan Department of Health and Human Services had logged 8,176 cases statewide, including 160 hospitalizations.
Of the confirmed cases with clinical information available, about 9 percent have required hospitalization, and no deaths have been reported. CDC and state health officials caution that because cyclosporiasis is frequently underdiagnosed, many people who recover without seeking medical care are never counted, meaning the true scale of the outbreak is likely larger than the confirmed numbers suggest.
Why the Source Is Still a Mystery
Investigators have not yet confirmed a specific food product, grower, or supplier. After conducting more than 1,000 patient interviews, Michigan health officials have identified lettuce and salad greens as a possible but unconfirmed common thread, according to Infection Control Today. Past outbreaks have been tied to imported fresh produce such as bagged salads, cilantro, basil, and berries, per Johns Hopkins Medicine, but no single product has been confirmed this year.
Cyclospora is also difficult to eliminate. According to CDC, EPA-registered disinfectants have not been proven effective against Cyclospora, and washing produce—even repeatedly—cannot guarantee removal.
What Healthcare Providers and Public Health Agencies Should Know
As the investigation continues, healthcare providers and public health agencies play a critical role in identifying cases, treating patients, and limiting further spread. CDC’s Health Alert Network recommends the following:
- Testing: Diagnosis requires stool testing to detect Cyclospora oocysts. Because shedding can be intermittent, multiple samples may be needed to reduce the risk of a false negative, per Infection Control Today.
- Treatment: CDC recommends a 7-to-10-day course of trimethoprim-sulfamethoxazole (TMP-SMX), with longer courses for immuno-compromised patients, according to the CDC HAN notice. Consult your medical provider on the best course of treatment.
- Reporting: Cyclosporiasis is nationally notifiable. Confirmed cases should be reported to local health departments within several days of diagnosis, per state guidance shared through the South Dakota Association of Health Officials (SDAHO).
- Infection prevention: Because cyclosporiasis does not spread from person to person, CDC notes that contamination risk in healthcare settings is low when patients are continent of stool. Standard precautions and hand hygiene remain the primary controls, per the CDC HAN notice.
What the Public Can Do
CDC’s guidance is candid that no single step fully eliminates risk, but several steps meaningfully lower it, per CDC’s prevention guidance:
- Wash hands with soap and water before and after handling raw produce.
- Rinse fruits and vegetables under running water before eating, cutting, or cooking them, even if labeled “prewashed.”
- Scrub firm produce, such as melons, cucumbers, and squash, with a clean produce brush.
- Cut away any bruised or damaged sections before eating.
- Refrigerate cut or peeled produce within two hours to limit further contamination.
Why This Matters Beyond the Headlines
Outbreaks like this one are a real-time stress test for the systems public health and healthcare organizations rely on every day. For Hagerty’s health sector clients working on emergency preparedness, infectious disease response, or public health emergency operations, the 2026 cyclosporiasis outbreak is a live example of how quickly a familiar, seasonal illness can outpace prior years and test coordination across jurisdictions.
Hagerty Can Help
The hardest communications problem in this outbreak is that no source has been confirmed. Hagerty helps public health departments:
- Build or refresh a Crisis and Emergency Risk Communication (CERC) plan before the next Health Alert lands, including message maps, spokesperson roles, and approval chains.
- Develop plain language, multilingual messaging on what is known, what is not, and the steps residents can take.
- Reach communities through trusted messengers and the right mix of channels: community partners, clinicians, social, and earned media.
For Hospitals and Health Systems: Staff Augmentation and Emerging Infectious Disease Programs
A surge six times higher than last year, with about 9 percent of cases hospitalized, strains already lean infection prevention, epidemiology, and lab teams. And cyclosporiasis is easy to miss, requiring a specific stool test a provider has to know to order. Hagerty helps hospitals and systems:
- Augment infection prevention, epidemiology, and emergency management staff during a surge, filling capacity gaps without pulling clinical staff off the floor.
- Stand up or strengthen emerging infectious disease programs, including surveillance workflows, protocols, and the infectious disease annex to the emergency operations plan.
- Support clinician awareness and plan for patient surge, so providers order the right tests, report promptly, and keep throughput steady when a seasonal illness outpaces its usual footprint.
Across the System: Coalitions, Coordination, and Exercises
Finally, outbreaks like this highlight that some of the greatest challenges occur at the points where organizations must work together. Timely case reporting, multi-state information sharing, and clinician awareness all play a critical role in an effective response. Hagerty helps healthcare coalitions and public health agencies:
- Strengthen case reporting and information-sharing pipelines so surveillance data moves cleanly between clinicians, local health departments, and states.
- Facilitate discussion-based and operational exercises around foodborne and emerging infectious disease scenarios, evaluating the coordination, communications, and surge decisions this outbreak is demanding in real time.
- Capture lessons learned through after-action reviews while the response is still fresh, so the next season starts from a stronger baseline.
Whether you are a health department drafting your next community update, a hospital watching case counts climb, or a coalition keeping every partner aligned, Hagerty Health can help you turn a fast-moving outbreak into a test your systems are ready to pass.