Cyclosporiasis Outbreak Slowing? Test-Makers See Hopeful Signs 2026

The cyclosporiasis outbreak in the US may be slowing, according to test-maker bioMerieux, which sees declining positivity rates in its syndromic trends data. This potential turning point comes as the outbreak has grown to more than 18,000 suspected and confirmed cases, the largest on record, with the Midwest hit especially hard.

Understanding the Cyclosporiasis Outbreak

Cyclosporiasis is an intestinal illness caused by the single-celled parasite Cyclospora cayetanensis. Outbreaks typically occur in summer months, often linked to contaminated fresh produce. This year's outbreak has been linked to iceberg lettuce from Taylor Farms' Mexico operations, affecting nine states.

The Centers for Disease Control and Prevention (CDC) has confirmed 6,707 cases acquired in the US, with an additional 11,500 suspected cases pending confirmation. The Midwest has borne the brunt, with public health officials working to trace the source and prevent further spread.

Test-Maker Data Offers Hope

bioMerieux, the French maker of a gastrointestinal panel that tests for 22 illnesses, published data showing a decline in total test positivity for parasites. John Osiecki, vice-president of medical affairs at bioMerieux, stated, “I’m feeling confident we’re heading in that direction, but we need to continue to monitor this as we go forward.”

The data reveals that parasite positivity peaked in mid-July at 15.6%, compared to just 2.9% in the same week in 2025. This sharp spike is an outlier, but the recent decline suggests the outbreak may be easing.

Key Caveats in the Data

However, there are important caveats. Heightened public awareness has led more people to get tested, and if many tests return negative, positivity rates could drop even while the outbreak persists. Osiecki acknowledges this, noting that people are requesting no lettuce in social settings due to cyclospora awareness.

CDC data, while slower to publish, offers higher certainty. The agency relies on interviews and laboratory confirmation, which takes longer but provides a more accurate picture. The discrepancy between rapid test data and official CDC counts highlights the challenges in real-time outbreak monitoring.

Comparison: bioMerieux vs. CDC Data

What This Means for Public Health

If the outbreak is indeed slowing, it could signal that contaminated products are being removed from the supply chain and public awareness is reducing exposure. However, health officials urge continued vigilance, as cyclosporiasis can have a long incubation period and cases may still emerge.

For consumers, the advice remains: wash produce thoroughly, avoid potentially contaminated lettuce, and seek medical care if symptoms like watery diarrhea, cramping, and fatigue persist.

Key Takeaways

• Test-maker bioMerieux reports declining parasite positivity, suggesting the outbreak may be slowing.
• The CDC has confirmed over 6,700 cases, with thousands more suspected.
• Iceberg lettuce from Taylor Farms' Mexico operations is linked to infections in nine states.
• Public awareness and testing behavior can skew positivity rates, so caution is needed.
• CDC data will provide definitive confirmation as it becomes available.

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