Cyclosporiasis Outbreak 2026: 1,645 Confirmed Cases in 34 States, With a Growing Cluster in Michigan, Ohio, West Virginia, and Kentucky

A rapidly expanding cyclosporiasis outbreak has prompted the CDC to issue a formal Health Alert Network notice, warning clinicians, laboratorians, and public health practitioners about a surge in domestically acquired cases outpacing last year's numbers by more than 6-to-1.

As of July 13, 2026, CDC has confirmed 1,645 laboratory-verified cases of cyclosporiasis in people who acquired the illness inside the US without any international travel in the preceding 2 weeks.¹ An additional 5,100 cases are awaiting further analysis to determine whether they qualify as domestically acquired. Cases have been reported from 34 states.¹ By the same date last year, only 249 cases had been confirmed nationally. As CDC notes in its Health Alert Network notice, "Because cyclosporiasis is often underdiagnosed and underreported, the true number of illnesses is likely higher than what has been reported to CDC.^1”

A Cluster at the Center

Within the broader national picture, investigators have identified a concentrated multistate cluster with epidemiological linkage among more than 400 cases in at least 4 Midwestern states: Michigan, Ohio, West Virginia, and Kentucky. The tighter connection between these cases suggests a common source exposure, though that source has not yet been confirmed. Sick people in this cluster reported symptom onset on or after June 22, 2026.^1,2

Michigan's Department of Health and Human Services has conducted more than 1,000 patient interviews as part of its investigation.³ Early results from those interviews point to lettuce or salad greens as a possible vehicle for transmission, though investigators have not made a definitive link to any specific product or supplier. "A specific food item has not yet been confirmed as the source," CDC stated on its outbreak investigation page.²

Who Is Getting Sick

Among the 1,645 confirmed cases, patients ranged in age from 2 to 95 years, with a median age of 44. Slightly more than half (56%) were female. Of those cases with available clinical information, 141 patients (9%) required hospitalization.² No deaths have been reported. While the illness is described by the CDC as something that "is not usually life-threatening, however, some people can become very ill and require hospitalization, health care facilities should be prepared for admissions that may not immediately raise suspicion for cyclosporiasis.”¹

The Diagnostic Challenge

Cyclospora cayetanensis, the microscopic parasite responsible for cyclosporiasis, is notoriously easy to miss in routine laboratory workups. Standard ova and parasite examinations may not reliably detect it. CDC is urging clinicians to specifically order Cyclospora testing on stool specimens when the illness is clinically suspected, and to consider PCR-based molecular testing where available, which offers improved sensitivity over conventional modified acid-fast staining.

Symptom onset typically occurs about one week after exposure, with a range of 2 to 14 days.^1-3 The hallmark presentation is watery diarrhea that can be frequent and prolonged, often accompanied by loss of appetite, weight loss, bloating, nausea, and fatigue. Without treatment, the illness follows a remitting-relapsing course that can stretch from days to more than a month. The recommended treatment for immunocompetent patients is 7 to 10 days of trimethoprim-sulfamethoxazole, with longer courses considered for those with immunocompromising conditions.

Implications for Infection Prevention in Health Care Settings

For infection preventionists, the CDC's disinfection guidance deserves careful attention. "Cyclospora is unlikely to be killed or inactivated by routine chemical disinfection," the agency notes in its HAN notice.² "No EPA-registered disinfectant products have been demonstrated to be effective against Cyclospora." When a patient is incontinent or diapered, the risk of environmental contamination increases. CDC recommends initially cleaning surfaces with detergent to remove visible soil, then mechanically scrubbing them before applying an EPA-registered hospital disinfectant.

Person-to-person transmission is unlikely given the parasite's life cycle, but standard precautions apply to all patient contact involving potential fecal material. Contact precautions are warranted for patients with gastroenteritis who are diapered or stool-incontinent. Soap-and-water handwashing, rather than alcohol-based hand rub, is preferred when hands are visibly soiled, with vigorous scrubbing for 15 to 20 seconds.

As the summer cyclosporiasis season continues through August 31, CDC is asking all providers to report confirmed cases promptly to local health departments and to conduct detailed food and travel histories with affected patients. The investigation into the source of both the multistate cluster and the broader national surge is ongoing.^1,2

1. Cyclosporiasis outbreak with unknown source. CDC. July 14, 2026. Accessed July 15, 2026. https://www.cdc.gov/cyclosporiasis/outbreaks/07-26/index.html.
2. Domestically acquired cyclosporiasis cases in multiple U.S. states, 2026. CDC Health Alert Network. July 14, 2026. Accessed July 15, 2026. https://www.cdc.gov/han/php/notices/han00531.html.
3. Michigan Department of Health and Human Services. MDHHS updates recommendations for cyclosporiasis prevention. Michigan.gov. July 13, 2026. Updated July 14, 2026. Accessed July 15, 2026. https://www.michigan.gov/mdhhs/inside-mdhhs/newsroom/2026/07/13/cyclo-3.