Cyclosporiasis Outbreak Spreads to 45 States, CDC Reports

A widespread outbreak of cyclosporiasis, a parasitic infection known for causing severe gastrointestinal illness, has now reached 45 states with 6,707 laboratory-confirmed cases since May 1, the Centers for Disease Control and Prevention reported. Health officials have linked the largest cluster to contaminated iceberg lettuce from central Mexico, prompting a major recall that has so far spanned nine states.

What Is Cyclosporiasis?

Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis, typically contracted through contaminated food or water. The most common symptom is watery, frequent, and sometimes explosive diarrhea, along with nausea, vomiting, fatigue, and stomach cramps. Symptoms generally appear about one week after exposure and can persist for weeks without treatment.

According to the CDC, 423 people — approximately 9% of confirmed cases — have been hospitalized, though no deaths have been reported. Patients range in age from 1 to 98 years, with a median age of 44, and 56% are female. The agency noted a six-week reporting lag between illness onset and case confirmation, meaning current figures likely underrepresent the outbreak’s true scale.

Outbreak by the Numbers

The CDC’s July 28 surveillance update documented domestically acquired cases in every state except Hawaii, Maine, Montana, New Mexico, and South Carolina. The agency is also aware of more than 11,500 additional cases that have not yet been laboratory-confirmed, primarily concentrated in Michigan and Ohio.

This year’s count is substantially higher than the 249 cases reported nationally during the same period in 2025, according to a CDC Health Alert Network notice issued July 14. The notice, distributed to clinicians and public health officials nationwide, warned that the true number of illnesses was likely higher than reported because many people recover without seeking medical care.

Michigan has emerged as the epicenter of the outbreak. The state reported over 10,000 cases as of July 29, according to the Detroit Free Press. Wayne County leads with 1,201 cases, followed by Washtenaw County with 773 and Oakland County with 710. Approximately 160 Michigan patients have been hospitalized. Ohio remains the second-hardest-hit state.

Source Identified: Recalled Lettuce

The U.S. Food and Drug Administration traced the largest multistate outbreak to iceberg lettuce grown by Taylor Farms in central Mexico. On July 17, Taylor Farms initiated a voluntary recall of all iceberg lettuce sourced from central Mexico, including products sold at retail stores and served in restaurants. The recalled items were distributed to at least 27 states between June 29 and July 16.

Illnesses from the lettuce outbreak have been confirmed in nine states: Illinois, Indiana, Kansas, Kentucky, Michigan, Ohio, Oklahoma, Pennsylvania, and West Virginia. The CDC and FDA continue to investigate multiple separate case clusters whose sources remain unidentified.

Official Response and Controversy

Health and Human Services Secretary Robert F. Kennedy Jr. stated at a July 21 press briefing that the outbreak is “under control,” citing the ongoing epidemiological investigation and the Taylor Farms recall. However, critics have pointed to the CDC’s decision in 2025 to scale back the Foodborne Diseases Active Surveillance Network (FoodNet), which reduced the number of foodborne pathogens under active tracking from six to just two. Cyclospora was one of the pathogens removed from mandatory monitoring. Sen. Jon Ossoff (D-GA) criticized the administration for these cuts, calling them “foolish” in light of the current outbreak.

Mexican health authorities have also disputed the FDA’s assertion that the outbreak originated in Mexico, requesting additional evidence to support the traceback investigation.

The CDC acknowledged that reporting gaps complicate the picture. “Cyclosporiasis cases may not be limited to these states with known cases,” the agency said in its update, as reported by USA Today. “The true number of people sick with cyclosporiasis was likely higher than the number reported. This is because some people recover without medical care and are not tested for Cyclospora.”

Challenges in Tracking the Parasite

Unlike bacterial pathogens such as E. coli and listeria, Cyclospora cannot be tracked using whole genome sequencing, making it significantly harder to identify outbreak sources. Standard ova and parasite exams may not reliably detect the parasite; specific PCR or modified acid-fast staining tests are required for accurate diagnosis. The long incubation period — up to 14 days — further complicates efforts to trace contaminated food back to its source.

What’s Next

With the summer cyclosporiasis season running through August 31, health officials expect case counts to continue rising as additional reports are processed. Consumers are advised to wash all fresh produce thoroughly and check for recalled iceberg lettuce products carrying label codes linked to the Taylor Farms recall. The CDC recommends that anyone experiencing prolonged or watery diarrhea seek medical attention, as the infection is treatable with a 7-to-10-day course of the antibiotic trimethoprim-sulfamethoxazole.

The outbreak has reignited debate over food safety surveillance funding and the adequacy of the nation’s systems for detecting emerging foodborne threats. The coming weeks will reveal whether the recall and public health interventions are sufficient to curb the spread of the parasite and prevent future outbreaks.