US — bioMerieux reported a decline in cyclosporiasis test positivity rates based on its Syndromic Trends data during the ongoing outbreak in the United States. The company’s surveillance indicates that while total suspected cases have surpassed 18,000, the proportion of tests returning positive results is decreasing.

The current cyclosporiasis outbreak is the largest on record in the US. As of late July, the number of suspected and confirmed cases has grown to more than 18,000. This figure represents an increase in the volume of individuals seeking testing for the parasitic infection.

Data from bioMerieux showed illness involving parasites peaked in mid-July with a 15.6% positivity rate. This metric reflects the percentage of tests conducted during that period that identified the parasite. For comparison, the parasite positivity rate for the same week in 2025 was 2.9%. The shift from 2.9% to 15.6% represents a rise of 12.7 percentage points over the one-year interval.

BioMerieux’s data, published as Syndromic Trends, shows a decline in total test positivity for cyclosporiasis following that mid-July peak. The downward trend suggests that the intensity of new infections may be moderating relative to the volume of testing. John Osiecki, vice-president of medical affairs at bioMerieux, expressed cautious optimism regarding this trajectory. "I’m feeling confident we’re heading in that direction, but we need to continue to monitor this as we go forward," he said.

The Centers for Disease Control and Prevention stated that people in at least nine states appeared to have connected cyclosporiasis cases. Public health officials have linked cyclosporiasis infections in nine states to iceberg lettuce from Taylor Farms’ Mexico operations. The CDC has confirmed 6,707 cases of cyclosporiasis acquired in the US.

The agency is waiting on data, including interviews, to confirm 11,500 additional suspected cases of cyclosporiasis. The sum of these confirmed and pending figures aligns with the total exceeding 18,000 reported by surveillance data.

The Farms lettuce linked to the outbreak was sold in 27 states. This distribution network covers a broad geographic area, complicating efforts to contain the spread. The New Hampshire department of health identified cases of people sickened by Farms lettuce from Mexico as recently as mid-July.

The New Hampshire cases were linked to a hospital cafeteria in Keene. New Hampshire is not currently considered part of the nine-state outbreak cluster, indicating that isolated incidents may be occurring outside the primary group of affected states.

Heightened public awareness has led more people to take cyclosporiasis tests, which could influence positivity rates. As consumers become more informed about the outbreak, they may seek testing even with mild or no symptoms, potentially diluting the positivity percentage. John Osiecki noted observable changes in consumer behavior driven by this awareness. "I’ve been in a lot of social settings, and I’ve heard people request not to have lettuce just because they’re aware of cyclospora," he said.

BioMerieux is a French maker of a panel that tests for 22 gastrointestinal illnesses. The specific panel used in these surveillance efforts tests for four parasites, not just cyclospora. This broader scope allows for the detection of other concurrent pathogens but focuses heavily on parasitic causes in this context.

The bioMerieux test costs $417. Medicare covers the bioMerieux panel only for people who are immunosuppressed. This coverage limitation means that many individuals paying for the test out-of-pocket may be doing so due to heightened concern rather than clinical necessity. The bioMerieux tests are more likely to be available in population centers than in rural areas, which may skew the geographic distribution of the data.

Syndromic Trends, the data publication by bioMérieux, was first launched in 2018 as a real-time surveillance tool to track infectious disease trends across the U.S. The platform provides near-real-time insights into disease activity, allowing for faster identification of trends than traditional reporting methods. Previous reports have documented legal and commercial responses to similar outbreaks. PureSource News previously reported that Farms recalled shredded iceberg lettuce in the U.S. outbreak. Additionally, PureSource News previously reported that attorney Marler filed lawsuits against Taco Bell and Farms in an Ohio Cyclospora outbreak.

Why It Matters

As the largest cyclosporiasis outbreak on record in the US, this event has driven over 18,000 suspected and confirmed cases linked to lettuce distributed across 27 states. The decline in test positivity rates suggests infection intensity may be moderating relative to the volume of testing, though heightened public awareness continues to influence testing behaviors. With Medicare coverage limited to immunosuppressed individuals, many patients face a $417 out-of-pocket cost for diagnostics that are more accessible in population centers than rural areas.