The maker of a popular lab test is cautiously optimistic that the cyclosporiasis outbreak in the US might be slowing down, which would be a relief to everyone who's been eyeing their salad with suspicion. The outbreak, caused by a single-celled parasite, has ballooned to over 18,000 suspected and confirmed cases by late July, making it the nation's largest on record. The Midwest has been hit especially hard, with public health officials linking infections in nine states to iceberg lettuce from Taylor Farms' Mexico operations. The Centers for Disease Control and Prevention (CDC) has confirmed that people in at least nine states appear to have connected cases.

John Osiecki, vice president of medical affairs at bioMerieux, the French maker of a panel that tests for 22 gastrointestinal illnesses, said, "I'm feeling confident we're heading in that direction, but we need to continue to monitor this as we go forward." That confidence comes with one big caveat - bioMerieux's data, published as Syndromic Trends, shows a decline in total test positivity, but heightened public awareness has led more people to take the tests. If a large number of people take the tests and have negative results, positivity rates could be pushed down even as the outbreak continues. However, Osiecki is hopeful the drop is real, driven by the same public 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," said Osiecki, proving that nothing says 'I'm fun at parties' like turning down a salad.

By contrast, CDC data takes longer but is published with a high degree of certainty. The CDC has confirmed 6,707 cases of cyclosporiasis acquired in the US and is waiting on data, including interviews, to confirm 11,500 more cases. Data from the test-maker showed illness involving "parasites" peaked in mid-July, with a 15.6% positivity rate. Cyclosporiasis is known to increase in summer months, but this peak is an outlier compared to the past two years. The same week in 2025 had a parasite positivity rate of 2.9%, which just goes to show that 2025 was a simpler time.

There are a few more caveats about bioMerieux's data: the panel tests for four parasites, not just cyclospora; Medicare, one of the nation's largest insurers, only covers the panel for people who are immunosuppressed (the test costs $417); and the tests are more likely to be available in population centers than in rural areas. So, if you're a rural, non-immunosuppressed person with $417 to spare, you're out of luck.

Whether or not the outbreak is slowing, some food safety researchers have warned that it may be larger than currently known. The Food and Drug Administration (FDA) is investigating several outbreaks that do not yet have a known cause, and the lettuce was sold in 27 states. In New Hampshire, not currently considered part of the outbreak, the state's department of health identified cases of people sickened by Taylor Farms lettuce from Mexico as recently as mid-July, linked to a hospital cafeteria in Keene. Because nothing says 'hospital food' like a side of cyclospora.