A parasitic outbreak is now spreading faster than the CDC can track. More than 4,000 cases of cyclosporiasis have been reported across 32 states, with the CDC confirming 843 domestically acquired cases as of July 9 and noting more than 1,500 additional cases still under analysis. Michigan is the hardest-hit state with more than 1,500 cases, followed by Illinois, New York, and Texas. No food source has been identified and no recall has been issued.
What Is Cyclosporiasis
Cyclosporiasis is an intestinal infection caused by Cyclospora cayetanensis, a microscopic parasite. It is not transmitted person to person. People get infected by consuming food or water contaminated with the parasite's oocysts (eggs).
In the United States, past outbreaks have been repeatedly linked to imported fresh produce including cilantro, basil, raspberries, snow peas, and mesclun lettuce. The summer timing is consistent with peak Cyclospora season, when contaminated produce from growing regions in Mexico and Central America enters the US supply chain.
How Many Cases and Where
National CDC data (as of July 9, 2026):
843 confirmed cases across 31 states, with 1,500+ additional cases under analysis. California was added to the list of affected states as of mid-July, bringing the confirmed total to 32 states. The hardest-hit states are Michigan, Illinois, New York, and Texas. The CDC notes that reported numbers significantly undercount actual cases.
Michigan (largest cluster):
More than 1,500 cases confirmed, concentrated in counties bordering Lake Erie, including Monroe, Lenawee, Washtenaw, and Wayne. Investigators are now examining a possible waterborne transmission route in addition to produce, based on the geographic clustering near Lake Erie. Michigan normally sees approximately 50 cyclosporiasis cases in an entire year.
The total case count exceeds 4,000 and is almost certainly an undercount. U.S. News reports the outbreak is spreading faster than the CDC can track. Cyclosporiasis requires specific stool testing that is not part of standard panels, meaning many cases go undiagnosed.
Symptoms
Symptoms typically begin 1 week after exposure and include:
- Watery diarrhea, sometimes described as explosive
- Frequent, sometimes urgent bowel movements
- Loss of appetite and weight loss
- Nausea and fatigue
- Stomach cramps and bloating
- Low-grade fever
Unlike norovirus, which typically resolves in 24 to 72 hours, cyclosporiasis symptoms can last weeks to months if untreated. The illness responds well to a specific antibiotic (trimethoprim-sulfamethoxazole). Standard diarrhea treatments do not address the parasite.
Of the nationally confirmed cases, hospitalizations have been reported in multiple states. Michigan and Ohio cases are being monitored particularly closely given the possible waterborne exposure route near Lake Erie. No deaths have been reported. Patients ranged in age from 5 to 86, with a median age of 42.
New Development: Possible Waterborne Transmission in Michigan and Ohio
A new angle emerged in July as investigators noted that cases in Michigan and Ohio are clustering in counties that border Lake Erie. This geographic pattern suggests a possible waterborne transmission route alongside the more typical foodborne route, though no specific water source has been confirmed.
This is significant because past Cyclospora outbreaks in the US have almost exclusively been foodborne, linked to contaminated produce. If confirmed, a waterborne component would require a different public health response and could explain why investigators have been unable to identify a single food source.
No Source Identified, No Recall Issued
As of July 14, 2026, investigators have not identified a common food source linking the cases. No food recall has been issued. The CDC has stated it has no evidence of a single multistate Cyclospora outbreak and is instead tracking several separate clusters.
This is a known challenge with Cyclospora outbreaks. The parasite is difficult to detect during routine food safety testing, and by the time an outbreak is identified, the implicated produce has often already been consumed. Investigations typically take weeks or months to trace a source, if one is found at all.
Based on prior outbreak patterns, fresh herbs (particularly cilantro and basil), leafy greens, and fresh berries are the highest-risk categories. People in affected states should consider washing fresh produce thoroughly and, if they develop symptoms, specifically asking their doctor to test for Cyclospora since it is not detected by standard stool tests.
When to See a Doctor
See a doctor if you develop watery diarrhea lasting more than a few days, especially if combined with significant fatigue, loss of appetite, or weight loss. Tell your doctor you are concerned about Cyclospora so they can order the correct test. The illness is treatable with prescription antibiotics.
Track Current Cyclosporiasis Activity
Virus Watcher is monitoring cyclosporiasis outbreak reports across all affected states.
- Cyclosporiasis in Michigan
- Cyclosporiasis in Illinois
- Cyclosporiasis in New York
- Cyclosporiasis in Texas
- Cyclosporiasis in California
- Cyclosporiasis in Ohio
- Cyclosporiasis in Massachusetts
- Cyclosporiasis in Florida
- View all cyclosporiasis state tracking
Download the Virus Watcher app to receive alerts when outbreak activity is confirmed in your state.
