The United States is experiencing the worst Cyclospora outbreak in its documented history. As of July 23, 2026, more than 11,000 confirmed or probable cyclosporiasis cases have been reported to the CDC, compared to 2,700 total cases in all of 2025 and approximately 4,500 in 2023, the previous single-year peak, according to NBC News reporting on the latest federal data. The scale of the 2026 outbreak has no historical precedent in the United States for this parasitic illness.
Federal investigators are simultaneously tracking multiple distinct clusters with different suspected sources, a complication that reflects both the scale and complexity of this outbreak. While the Taylor Farms iceberg lettuce recall linked to Taco Bell restaurants in five states remains the most clearly traced cluster, investigators have confirmed that this single-source cluster does not explain the full national case count. Multiple other clusters, including a new 72-case cluster identified by the FDA on July 23 with no food source yet identified, remain under active investigation.
Why This Matters
The record-breaking nature of this outbreak cannot be attributed to a single recall or a single contaminated product. The national case count has already exceeded any full prior season before the Cyclospora transmission season, which the CDC defines as May 1 through August 31, has ended. That means additional cases are still expected over the coming weeks.
For MedicalDaily readers, this matters because cyclosporiasis is not a mild illness. Without antibiotic treatment, the diarrheal disease caused by the Cyclospora cayetanensis parasite can persist for weeks, cycling through periods of feeling better and worse. It is treatable, but it requires a diagnosis, and that diagnosis requires a clinician to specifically order a Cyclospora stool test, because routine stool cultures do not detect this parasite. Many people have likely been sick with this outbreak and never received a correct diagnosis.
The multi-cluster nature of this outbreak also means that the food avoidance advice linked to the Taylor Farms iceberg lettuce recall does not fully protect consumers. There are other sources of illness still circulating that have not yet been publicly identified.
What We Know So Far
The CDC's July 23, 2026, outbreak data, as reported by Axios, Food Safety Magazine, and The New York Times, show 4,173 laboratory-confirmed domestic cases with an additional 7,400-plus under investigation. Michigan has reported 7,171 cases, and Ohio has reported more than 2,000. These numbers have been rising daily throughout July.
The multistate outbreak cluster centered in Michigan, Ohio, Indiana, Kentucky, and West Virginia, and linked through traceback to shredded iceberg lettuce from Taylor Farms de Mexico supplied to Taco Bell, represents 1,644 confirmed cases in the lettuce-linked cluster alone. That single cluster exceeds the scale of every prior Cyclospora outbreak on U.S. record, which according to CNN previously peaked at approximately 1,500 cases in a 1996 raspberry-linked outbreak.
On July 23, the FDA added a new Cyclospora cluster to its CORE investigation table, involving 72 cases with an unidentified food source. This is in addition to the ongoing Taylor Farms investigation and reflects the multi-front nature of the national outbreak.
Investigators at the CDC issued a national Health Alert Network advisory on July 14, 2026, noting that 2026 cases are substantially higher than the 249 cases reported nationally over the same period in 2025. The agency urged clinicians across all 47 nationally notifiable states to specifically request Cyclospora diagnostic testing when evaluating patients with prolonged watery diarrhea, since standard stool exams often miss the parasite.
Where the Risk Is Highest
Michigan and Ohio carry by far the heaviest case burden, with Michigan's estimated infection rate approaching 15 per 100,000 people based on midpoint case count estimates and state population figures, according to Axios. Indiana, Kentucky, West Virginia, North Carolina, Texas, New York, Illinois, and Virginia have also reported elevated case counts beyond what would be expected in a normal year.
The unidentified clusters under investigation mean geographic risk is not limited to the five-state lettuce outbreak zone. People across the United States who develop prolonged watery diarrhea in the coming weeks, regardless of whether they ate at Taco Bell or consumed iceberg lettuce, should raise Cyclospora as a diagnostic possibility with their health care provider.
Multiple food safety experts quoted in national media, including CNN's coverage, suspect that more than one food or water source is fueling the outbreak nationwide. Mexican health authorities said on July 21 they have found no evidence so far that the iceberg lettuce from Mexico is the definitive contamination source for the lettuce-linked cluster, and the investigation into the contamination mechanism remains open.
What Doctors and Experts Say
Dianna Blau, acting chief of the CDC's Parasitic Disease Branch, told NBC News that the United States reported 2,700 cyclosporiasis cases in all of 2025, and that 2026 has already far exceeded that total, with at least a month of transmission season remaining.
"When we started seeing cases of persistent diarrhea showing up, we knew something was going on," said Dr. Brian Kaminski, vice president of medical affairs at ProMedica Health System in Michigan and Ohio. Kaminski described the clinical pattern: patients presenting with prolonged, debilitating diarrhea that clinicians had to specifically test for Cyclospora to detect.
Several U.S. senators have written to Health Secretary Robert F. Kennedy Jr. urging that Cyclospora surveillance be restored to the FoodNet program. Experts have stated that while those cuts are problematic for long-term surveillance capacity, they did not cause the current outbreak.
What the Evidence Shows and What It Does Not
The national Cyclospora case count comes from CDC's national notifiable disease surveillance system. Laboratory-confirmed cases require specific Cyclospora stool testing and represent a fraction of actual illnesses, as many people recover without being tested and others receive incorrect diagnoses. The true number of illnesses is certainly higher than the reported figures. The linkage between the Taylor Farms lettuce and the five-state cluster rests on epidemiological evidence, including the finding that 90 percent of interviewed Michigan patients reported eating iceberg lettuce and the traceback of the supply chain, despite the FDA's reported retraction of a positive laboratory test result from Taylor Farms lettuce. Multiple other clusters remain under investigation with no food source identified, meaning the full scope and source structure of the outbreak is not yet known.
Who Faces the Greatest Risk
All people who have consumed fresh produce, particularly iceberg lettuce from recalled sources, in the states with the highest case burdens face elevated risk. People with weakened immune systems, including transplant recipients, people receiving cancer treatment, HIV-positive individuals, and pregnant people, face the greatest risk of prolonged or severe illness and complications. Adults over 65 and children under 5 also face a higher risk of severe dehydration. The illness does not spread person-to-person.
Symptoms and Warning Signs to Watch For
Cyclosporiasis symptoms typically begin one week after exposure, ranging from two to 14 days. The hallmark is prolonged watery diarrhea that may be explosive, accompanied by loss of appetite, weight loss, bloating, abdominal cramps, nausea, and fatigue. A low-grade fever may occur. Without treatment, symptoms can last for weeks and may wax and wane.
Anyone with prolonged diarrhea lasting more than a few days should see a health care provider and specifically ask to be tested for Cyclospora. The antibiotic treatment, trimethoprim-sulfamethoxazole taken for 10 days, is highly effective. Standard over-the-counter antidiarrheal medications do not treat the underlying infection.
What You Can Do Now
Stop eating and discard any iceberg lettuce from Taylor Farms de Mexico that you have purchased, particularly Marketside Iceberg Salad and Shredded Lettuce sold at Walmart with best-by dates through August 3, 2026. Avoid shredded iceberg lettuce at Taco Bell locations in the five-state outbreak zone: Indiana, Kentucky, Michigan, Ohio, and West Virginia.
Wash all fresh produce thoroughly under clean running water before eating. Pre-washed bagged lettuce should be rewashed; the CDC acknowledges this may not fully eliminate Cyclospora but provides additional protection. Anyone who has been experiencing prolonged watery diarrhea in the past several weeks should contact a health care provider and specifically request Cyclospora stool testing, since routine panels do not include it. People in Michigan and the surrounding outbreak states should have a lower threshold for seeking care given the extent of community spread.
Cost and Access: What Patients Should Know
The antibiotic used to treat cyclosporiasis, trimethoprim-sulfamethoxazole, is a generic drug available at low cost at most pharmacies and covered by most insurance plans, including Medicaid. People without a primary care provider can contact their local or county health department for guidance on testing and referral. Many county health departments are actively tracking this outbreak and can direct residents to appropriate care.
What Happens Next
The CDC is updating its Cyclospora surveillance data daily through state health departments and expects cases to continue through August. The FDA's CORE investigations into the unlinked clusters are ongoing. A full outbreak closure report, similar to what was recently issued for the moringa leaf powder Salmonella outbreak, will not be available until investigations are complete and case counts have declined. MedicalDaily will continue updating its Cyclospora coverage as the situation evolves.
The Bottom Line
The 2026 Cyclospora outbreak is the worst in the history of U.S. surveillance, with more than 11,000 cases already reported and at least a month of transmission season remaining. The Taylor Farms iceberg lettuce recall addresses the most clearly traced cluster, but multiple unlinked clusters with unidentified food sources mean additional cases are still occurring. Anyone with prolonged diarrhea should seek testing specifically for Cyclospora, since standard stool panels miss the parasite. Follow the recall guidance, watch for symptoms, and rely on CDC and state health department updates rather than social media for the latest information.
