The Centers for Disease Control and Prevention is warning that the true number of cyclosporiasis infections in the United States could be dramatically higher than the official tally, as thousands of suspected cases await final confirmation.
According to the CDC, 1,645 confirmed cases of the parasitic illness have been reported across 34 states since May 1. That marks a near-sixfold increase over the 249 cases reported during the same period last year. But the agency cautioned in a recent alert to health care providers that more than 5,100 additional cases require further testing to determine whether the illness was locally acquired.
The discrepancy highlights a persistent gap in surveillance and diagnostic capacity, raising concerns among public health experts that the outbreak is far larger than what is being captured. Cyclosporiasis, caused by the Cyclospora cayetanensis parasite, triggers severe gastrointestinal distress—including watery diarrhea, cramping, and fatigue—and can last weeks if untreated.
The CDC has been investigating the outbreak for months, with a particular focus on contaminated produce. Previous cyclospora outbreaks have been linked to imported fresh vegetables and herbs, such as cilantro, basil, and salad greens. The agency has not yet identified a specific source for the current wave, though a Michigan parasite outbreak tied to salad greens has been a key part of the probe.
Testing Bottlenecks and Underreporting
Public health officials say the gap between confirmed and suspected cases is partly due to the complexity of testing for cyclospora. Unlike many bacterial infections, the parasite requires specialized lab techniques that are not routinely used in all hospitals or clinics. Many patients may not even seek medical care, and those who do often face delays in diagnosis.
“We are likely seeing only the tip of the iceberg,” said Dr. Linda Thompson, an infectious disease specialist at the University of Minnesota. “The CDC’s warning about the 5,100 pending tests underscores how many cases are slipping through the cracks.”
The CDC has urged clinicians to consider cyclospora in patients with prolonged diarrhea and to report suspected cases promptly. The agency also noted that the illness is not typically transmitted from person to person, meaning the primary risk remains contaminated food.
Outbreak Spread and Government Response
While the outbreak has been reported in states from coast to coast, some regions have seen a heavier burden. The cyclospora outbreak that surged past 1,000 cases earlier this summer has continued to expand, with Michigan alone reporting nearly 1,000 cases in what officials have called an unprecedented event.
The House Ethics Committee has not been involved in the outbreak response, but lawmakers have pressed the CDC for faster action. In a recent hearing, several members of Congress questioned whether the agency’s surveillance system is adequate to detect foodborne outbreaks in real time.
The CDC has deployed additional epidemiologists to affected states and is working with the Food and Drug Administration to trace the source of contaminated produce. Meanwhile, health officials are cautioning consumers to thoroughly wash fresh fruits and vegetables, especially those imported from regions where cyclospora is endemic.
For now, the true scale of the outbreak remains uncertain. As testing continues, the CDC’s alert serves as a stark reminder that the numbers on the dashboard may not tell the full story.
