The Centers for Disease Control and Prevention says the outbreak has reached a level far exceeding recent years, with investigators now working across dozens of states to determine exactly what is making so many people sick.
The CDC announced Tuesday that 1,645 people have been confirmed to have cyclosporiasis after becoming infected in the United States since May 1, while more than 5,100 additional cases are under investigation.
Combined, health officials are now reviewing more than 7,000 possible cases across the country.
The CDC said confirmed infections have been identified in 34 states, with several separate investigations underway.
A major outbreak centered in Michigan and Ohio has now been epidemiologically linked to cases in West Virginia and Kentucky, suggesting those infections may share a common source.
Federal health officials say the number of confirmed cases is already more than six times higher than it was at this point last year.
If the confirmed and suspected cases are combined, this year’s total is roughly 27 times higher than the same period in 2025.
“This is much, much higher than what we’ve seen last year or the year before,” said Dr. Gwen Biggerstaff, deputy director of the CDC’s Division of Foodborne, Waterborne, and Environmental Diseases.
“It’s a very big shift.”
The parasite, Cyclospora cayetanensis, causes cyclosporiasis, a gastrointestinal illness that commonly produces severe watery diarrhea, abdominal cramping, bloating, nausea, fatigue and loss of appetite.
Symptoms can last for several weeks and often return after initially improving.
According to CDC data, approximately one out of every eleven confirmed patients has required hospitalization.
No deaths have been reported.
Investigators believe at least 400 confirmed cases spanning Michigan, Ohio, West Virginia and Kentucky appear to be connected.
Michigan has emerged as the hardest-hit state, reporting more than 3,300 cases during its investigation.
State officials have interviewed more than 1,000 patients and say the evidence currently points toward lettuce or salad greens as a possible source.
However, investigators emphasized that no specific produce item, grower, supplier or distributor has been identified.
The CDC likewise says multiple investigations remain active and that no single nationwide source has been confirmed.
As concern has grown, Taco Bell announced Tuesday that it is voluntarily removing certain ingredients from menus at select restaurants as a precaution.
The company stressed that public health officials have not linked Taco Bell, any ingredient, supplier or restaurant to the outbreak.
“Public health officials have not confirmed a link to Taco Bell or any specific ingredient, supplier, restaurant or retailer,” the company said in a statement.
Cyclosporiasis is generally spread by consuming food or water contaminated with the microscopic parasite rather than through person-to-person contact.
Previous U.S. outbreaks have been traced to fresh produce, including raspberries, cilantro, basil and salad greens.
Federal investigators continue working with state health departments to identify the source of the current outbreak.
NEW: Infectious disease doctor advises avoiding fresh produce — even if washed — as the explosive diarrhea outbreak spreads rapidly throughout the U.S.
— Polymarket (@Polymarket) July 14, 2026
Until that source is identified, health officials are urging anyone who develops persistent watery diarrhea or other symptoms consistent with cyclosporiasis to contact a healthcare provider, particularly if symptoms continue for several days or lead to dehydration, CNN reported.
With confirmed cases continuing to climb and thousands more still under investigation, the CDC says the scope of the outbreak remains fluid as investigators work to determine exactly where the contamination originated.
