In the midst of one of the largest cyclospora outbreaks the United States has seen in recent years, a moment of scientific correction arrived: a lettuce sample from Taylor Farms that had seemed to confirm the source of widespread illness was declared a false positive by FDA laboratory experts. The announcement offered partial relief but no resolution, as more than 1,600 federally confirmed cases — and over 5,000 in Michigan alone — continued to remind public health officials that the parasite's true origin remained elusive. It is a familiar tension in the story of foodborne illness: the tools
FDA Says Taylor Farms Lettuce Tested Positive for Cyclospora Was False Positive
Over 1,600 people have been sickened across 34 states in a multistate cyclospora outbreak linked to contaminated lettuce, with Michigan reporting over 5,000 cases.
The parasite doesn't always show up the same way twice.
Mark
So the test came back positive, and then it didn't. How does that happen?
Mimi
Cyclospora is genuinely hard to detect in a lab. The parasite doesn't always show up the same way twice. The FDA's experts looked at the sample again and realized what looked like a positive signal wasn't actually the parasite—it was noise, essentially.
Mark
But the outbreak is still real. People are still sick.
Mimi
Absolutely. Over 1,600 confirmed cases across 34 states, and Michigan alone is reporting over 5,000. The false positive just means this particular sample wasn't the smoking gun they thought it was.
Mark
So they still don't know exactly where it came from?
Mimi
They've narrowed it down. The FDA's traceback investigation pointed to one specific farm in central Mexico that supplies less than 1 percent of U.S. iceberg lettuce. Taylor Farms pulled all lettuce from that region indefinitely.
Mark
And the restaurants and stores—they're removing products?
Mimi
Yes. Taco Bell removed the affected lettuce from five states. Walmart pulled bagged salads from over two dozen states, though they said their products weren't directly implicated.
Mark
What makes cyclospora so hard to catch?
Mimi
It's a parasite, not a bacteria. It causes severe, long-lasting diarrhea. These outbreaks tend to happen in late spring and summer, and they've historically been tied to fresh produce—salads, herbs, berries. This one is one of the largest in recent years.
Le Pouls
- A cyclospora outbreak first detected in May has now reached 34 states, sickening over 1,600 people by federal count and more than 5,000 in Michigan alone — numbers that signal a public health crisis still very much in motion.
- The FDA's declaration of a false positive on Taylor Farms lettuce removed one apparent answer just as millions of people were looking for reassurance about what was safe to eat.
- Taylor Farms pulled all iceberg lettuce from a central Mexican growing region indefinitely, and Taco Bell completed removal of affected products from restaurants across five Midwestern and Appalachian states.
- Walmart moved preemptively, pulling four Marketside bagged salad products from shelves in over two dozen states even without direct evidence linking its products to the outbreak.
- No deaths have been reported, but the investigation remains active — the false positive cleared one suspect without identifying another, leaving the source of thousands of illnesses still unconfirmed.
In the midst of one of the largest cyclospora outbreaks the United States has seen in recent years, a moment of scientific correction arrived: a lettuce sample from Taylor Farms that had seemed to confirm the source of widespread illness was declared a false positive by FDA laboratory experts. The announcement offered partial relief but no resolution, as more than 1,600 federally confirmed cases — and over 5,000 in Michigan alone — continued to remind public health officials that the parasite's true origin remained elusive. It is a familiar tension in the story of foodborne illness: the tools we use to find answers are themselves imperfect, and certainty, when lives are at stake, is rarely swift.
The FDA announced Sunday that a Taylor Farms lettuce sample which had initially tested positive for cyclospora was, in fact, a false positive. Laboratory experts re-examined the result and determined that what appeared to be cyclospora amplification was not genuine — a finding the agency attributed to the inherent difficulty of reliably detecting the parasite. As of that Sunday, no confirmed positive results had emerged from any product testing.
The correction arrived against the backdrop of a serious and still-unresolved outbreak. First identified in May, the multistate cyclospora event had spread across 34 states, with the CDC counting more than 1,600 confirmed cases and Michigan's state health department reporting over 5,000 on its own. No deaths had occurred, but the illness — which causes prolonged, severe watery diarrhea — had affected thousands across the country.
Earlier that week, Taylor Farms had voluntarily pulled all iceberg lettuce from a specific central Mexican region after FDA investigators identified a single independent farm, representing less than one percent of the national iceberg supply, as the likely source. The company committed to keeping that region's lettuce off the market indefinitely. Taco Bell, which had distributed the affected lettuce to restaurants in Indiana, Kentucky, Michigan, Ohio, and West Virginia, confirmed it had completed removal of the implicated products.
Walmart also acted over the weekend, removing four Marketside bagged iceberg salad products from stores in more than two dozen states as a precautionary measure, even without evidence directly linking its products to the outbreak. Cyclospora outbreaks typically emerge in late spring and summer and have historically been tied to fresh produce — bagged salads, cilantro, raspberries, and green onions among them. This outbreak ranked among the largest the country had seen in recent years.
Taylor Farms said Sunday that its concern remained with those who had fallen ill and that it would continue cooperating with public health authorities. The false positive finding narrowed the evidentiary picture without closing the investigation — the outbreak, with its thousands of cases and no confirmed source, remained an active and urgent public health matter.
The Food and Drug Administration announced Sunday that a sample of lettuce from Taylor Farms that had initially tested positive for cyclospora was, in fact, a false positive. The agency's laboratory experts had re-examined the sample and determined that what appeared to be cyclospora amplification was not genuine—a conclusion the FDA attributed to the inherent difficulty in detecting the parasite reliably. As of that Sunday, the agency said it had found no confirmed positive results from any product testing for cyclospora.
The false positive announcement came as a measure of relief in the midst of an outbreak that had already sickened thousands. The multistate cyclospora outbreak, first identified in May, had spread across 34 states and affected more than 1,600 people according to CDC counts, though state health departments reported substantially higher numbers. Michigan alone had documented more than 5,000 confirmed cases by Friday. No deaths had been reported.
Taylor Farms had voluntarily removed all iceberg lettuce from a specific region in central Mexico on Friday, after the FDA's investigation pointed to a single independent farm—representing less than 1 percent of the nation's iceberg lettuce supply—as the likely source. The company said it would keep the region's lettuce off the market indefinitely. The contaminated lettuce had been distributed to Taco Bell restaurants across Indiana, Kentucky, Michigan, Ohio, and West Virginia. Taco Bell confirmed Friday that it had completed the removal of the affected Taylor Farms products from its locations.
Walmart also took action over the weekend, pulling four Marketside bagged iceberg lettuce salad products from stores in more than two dozen states, though the retailer noted there was no evidence that its own products had been affected by the outbreak investigation. The company's move appeared to be precautionary.
Cyclospora is a parasite transmitted through contaminated food and water. The infection, called cyclosporiasis, produces prolonged watery diarrhea that can be severe. Outbreaks typically emerge in late spring and summer and have historically been connected to produce items like bagged salads, cilantro, basil, raspberries, snow peas, and green onions. The current outbreak represented one of the largest cyclospora incidents the country had experienced in recent years.
Taylor Farms said Sunday that its thoughts remained with those who had fallen ill and that the company remained committed to working with public health authorities as the investigation continued. The false positive finding did not end the outbreak investigation—it simply meant that the particular sample that had triggered concern was not actually positive. The outbreak itself, with its thousands of confirmed cases spread across dozens of states, remained an active public health matter.
Citations marquantes
Due to the complexity in detection of Cyclospora, FDA laboratory experts re-reviewed the sample results and have concluded that the finding does not represent true amplification and should be considered a false positive.— FDA statement
Our thoughts remain with everyone who has fallen ill in this outbreak. We are committed to working with public health authorities as the ongoing outbreak investigation continues.— Taylor Farms statement
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