Cyclosporiasis outbreak shows signs of slowing in US

Diagnostic testing data is pointing to a possible early slowdown in the current U.S. cyclosporiasis outbreak, even as the overall case burden remains historically high. The outbreak has reached a record 18,000 suspected and confirmed infections as of late July, according to the figures cited in the latest updates.

BioMerieux, a major supplier of gastrointestinal diagnostic panels used in clinical settings, reported that parasite positivity rates climbed through early summer and peaked at 15.6 percent in mid-July. The company said the rate has since started to trend lower, a shift that could indicate reduced transmission or a changing testing mix.

BioMerieux testing signals a peak, but interpretation is complex The 15.6 percent peak is a sharp departure from the 2.9 percent positivity rate recorded in the same period in 2025, underscoring how unusual this season’s outbreak has been. However, analysts cautioned that positivity data can move for reasons that do not reflect underlying infections in the community.

One concern cited is that heightened public awareness may be driving more people to seek testing, including individuals without symptoms. If testing volumes rise faster than true infections, the positivity rate could fall even while absolute case counts remain elevated.

Another limitation is that the BioMerieux panel referenced in the updates screens for four different parasites. Because the metric captures parasite positivity across that panel, it may not cleanly isolate cyclospora-specific changes over time.

Produce-linked exposure and multi-state reach

Officials have linked transmission to consumption of contaminated produce, with iceberg lettuce sourced from Taylor Farms’ operations in Mexico identified as connected to infections. Cases associated with this link have been reported across nine states, reflecting a distribution footprint that can spread exposure beyond a single local area.

While the apparent downtrend in positivity offers a possible sign of easing conditions, health agencies have stressed that confirmation and attribution require careful review. The pathway of infection remains consistent with prior cyclosporiasis patterns described by public health authorities: illness occurs after ingesting contaminated food items.

CDC case totals lag private indicators as investigations continue The Centers for Disease Control and Prevention has confirmed 6,707 domestic cases to date, while an additional 11,500 cases are currently under investigation. The difference reflects the gap between faster-moving private-sector diagnostic signals and the more stringent federal verification process, which can take longer as evidence is reviewed and classified.

At the same time, the FDA is continuing to investigate multiple outbreaks where the origins are not yet known. Public health officials have said the true number of infections could be higher than what is currently captured in official reporting, particularly when investigations are still active and exposures have not been fully identified.

For now, the trajectory through the rest of the summer remains uncertain, with early diagnostic deceleration weighed against changing testing behavior, panel-level measurement limits, and the time required for federal confirmation.