HEALTH
It began, as these things always do, with a handful of people who could not stop being sick. By mid-July, four states — Michigan, Ohio, West Virginia and Kentucky — had reported more than 400 people infected with a microscopic parasite most Americans have never heard of. By the last week of July, the count was 1,947 across nine states. By early August, 6,358 across fifteen. By August 27, the Centers for Disease Control and Prevention put the figure at 11,458 laboratory-confirmed illnesses across twenty states, with at least 495 hospitalisations and two deaths.
On September 3, the CDC updated its investigation page to say something that reads like relief and lands like a shrug: it is reducing the frequency of its web updates as new case reports decline. The weekly rhythm that had defined the summer is over.
What is not over is the question at the centre of it. In the largest cyclosporiasis outbreak the United States has ever recorded, investigators have never once found the parasite in the food.
THE PARASITE NOBODY TESTS FOR
Cyclospora cayetanensis is not a bacterium. It is a single-celled parasite, and almost everything about it makes it a public health nightmare.
It cannot be grown in a laboratory. Unlike E. coli or Salmonella, which investigators can culture from a sample and sequence in days, Cyclospora needs a human host to reproduce. Scientists cannot simply put it in a dish and confirm what they are looking at. Whole genome sequencing — the gold standard that cracks most modern foodborne outbreaks — cannot currently be used on this parasite at all.
It hides. The infectious oocysts lodge in microscopic crevices on the surface of produce, where they resist rinsing. Washing your salad does not reliably remove it. Freezing does not kill it. Only heat does, at around 158°F — which is precisely the temperature no one applies to shredded iceberg lettuce.
It is present in tiny numbers, meaning food samples have to be enormous to have any chance of catching it.
And it is slow. Symptoms begin anywhere from two days to two weeks after exposure. It can take up to six weeks to confirm that a sick person belongs to a particular outbreak. By the time investigators know they have a problem, the contaminated food has been eaten or thrown away.
Put those facts together and you get the defining feature of this outbreak: the case against the lettuce rests entirely on traceback records and patient interviews, not on a laboratory finding in the food.
THE FALSE POSITIVE THAT CHANGED NOTHING
For two days in July, it looked like investigators had caught a break.
A sample of Taylor Farms shredded lettuce collected at the border tested positive for Cyclospora. Then, on July 19, the FDA announced the result was a false positive that "does not represent true amplification." The agency withdrew it and said it did not change the investigation's conclusions.
The recall stayed in place. It is still in place.
It is tempting — and food companies have been known to encourage the temptation — to read "no positive sample" as "the food was fine." With this parasite, that inference simply does not hold. A negative or withdrawn result is not evidence of safety when the organism in question is nearly undetectable by design.
What investigators had instead was arguably stronger. The FDA's traceback converged on a single supplier: Taylor Farms de México, a central-Mexico-based processor. And the Michigan Department of Health and Human Services, analysing food exposure details from 190 early cases who had eaten at Taco Bell, found that 90 per cent of those interviewed reported eating iceberg lettuce.
Ninety per cent. From an ingredient-level analysis of the meals they actually ordered.
The FDA has continued sampling. In its August 27 update, the agency said onsite inspections and sampling at iceberg lettuce growers and at the processing facility in Mexico, coordinated with Mexican officials, were ongoing. No product sample has tested positive.
TIMELINE OF A SUMMER EPIDEMIC
The sequence of events reads like a slow-motion collision.
Mid-June: a new Cyclospora cluster appears on the FDA's CORE outbreak table, signalling an active federal investigation. The outbreak's own earliest illness onset would later be dated to June 14.
Early July: Michigan's case count reaches 572 and keeps climbing.
July 9: Taco Bell pulls fresh produce, including lettuce, from restaurants in the affected states.
July 14: the CDC issues a Health Alert Network advisory, reporting 1,645 confirmed and more than 5,100 probable cases nationwide.
July 16–17: the CDC links shredded iceberg lettuce served at Taco Bell to a five-state outbreak. The FDA traces it to a single central-Mexico supplier. Taylor Farms de México recalls all iceberg lettuce sourced from central Mexico — foodservice and retail alike.
July 19–20: the FDA declares its one positive sample a false positive.
July 24: five states become nine. The count reaches 1,947 with 98 hospitalisations.
July 28: a member of Congress formally questions Taylor Farms about the outbreak. Separately, North Carolina reports a distinct Cyclospora cluster linked to parsley and cilantro.
July 30: the CDC's combined confirmed-and-possible count passes 18,000, with 6,707 laboratory-confirmed. Six separate Cyclospora investigations sit on the FDA's CORE table simultaneously.
August 3: the first two deaths are reported, both in Michigan, both in people with underlying health conditions.
August 5: the CDC broadens the outbreak definition. It had been counting only Taco Bell diners; now it counts anyone who ate the recalled Taylor Farms lettuce from any source. The count leaps to 6,358 across fifteen states as six states are added at once.
August 13: 9,481 cases in seventeen states, with Maine and Massachusetts added.
August 20: 10,930 cases, 454 hospitalisations.
August 27: 11,458 cases in twenty states, with Georgia, Tennessee and Texas added. 495 hospitalisations. Onset dates now extend to August 15.
September 3: the CDC leaves the national figures unchanged and announces it will stop weekly updates.
THE MICHIGAN PROBLEM
Here is a number that stops people mid-sentence. Michigan alone has counted 14,718 cyclosporiasis cases.
That is more than the entire national confirmed total. It is not a mistake, and it is not a contradiction — it is two agencies answering two different questions.
The Michigan Department of Health and Human Services counts every cyclosporiasis case reported during its outbreak investigation, including probable ones. The CDC and FDA report only laboratory-confirmed cases they have specifically tied to this outbreak. As of September 3, Michigan's figure stood at 14,718 cases and 366 hospitalisations, still with two deaths. Both figures are correct.
The gap between them is the honest measure of how much of an outbreak like this stays invisible. And even Michigan's number is an undercount, because many people with cyclosporiasis never get tested at all.
The CDC says so explicitly: the true number of sick people is likely higher than the number reported, and the outbreak may not be limited to the states with known illnesses. Some people recover without medical care. Some recent illnesses have not been reported yet.
Michigan lifted its broad precautionary advisory against bagged salad mixes on August 6, telling residents that new case reports and diarrhoea-related emergency department visits were declining. The national recall remained — and remains — in effect.
WHAT THIS ILLNESS ACTUALLY DOES TO YOU
Most food poisoning is a wretched forty-eight hours. Cyclosporiasis is not most food poisoning, and this is the part that catches people out.
The characteristic symptom is watery diarrhoea that comes and goes — it eases, you assume you are recovering, and it returns. Alongside it: loss of appetite, significant weight loss, cramping, bloating, nausea and profound fatigue.
Untreated, symptoms can last weeks to more than a month, and they can relapse. People have described losing a stone and most of a summer to it.
The standard treatment is an antibiotic — trimethoprim-sulfamethoxazole, sold as Bactrim or Septra. People with a sulfa allergy have limited alternatives, and that is a real clinical problem rather than a footnote.
Serious illness is uncommon in otherwise healthy adults. But the two Michigan deaths were both in people with underlying health conditions, and cyclosporiasis can be genuinely dangerous for the very young, the elderly, and anyone whose immune system is already compromised. Four hundred and ninety-five people did not go to hospital for a mild tummy upset.
One piece of reassurance worth stating plainly: Cyclospora is not contagious between people. After it passes in stool it needs days to weeks in the environment before it becomes infectious, so it spreads through contaminated food and water, not through casual contact. You cannot catch it from your partner.
WHAT THIS MEANS FOR YOU
The best-by dates on the recalled Taylor Farms de México products ran from July 18 to August 3, 2026. They have passed. The CDC says the product should no longer be in stores or restaurants. If you somehow still have a bag in a fridge or freezer, throw it out — double-bagged, so no one else eats it — or return it for a refund.
At retail, the recalled product was sold under the Marketside brand at Walmart: Marketside Iceberg Salad in 12-ounce and 24-ounce bags, and Shredded Lettuce in 8-ounce and 16-ounce bags. Foodservice products were listed separately. The recalled lettuce reached 31 states, and the FDA notes distribution may have gone further still.
The single most important practical point: eating at Taco Bell was never the only route of exposure. The CDC broadened the outbreak definition on August 5 precisely because the same lettuce reached supermarkets and other restaurants. If you ate iceberg lettuce anywhere during the outbreak window and got ill, you may be part of this.
If you are sick now, or were and never got an answer, the crucial instruction is this: ask your doctor specifically for a Cyclospora test. It is not part of a standard stool panel. A laboratory has to run a specific test — a special stain or a molecular PCR panel — and physicians frequently have to request it by name. People have gone weeks misdiagnosed with viral gastroenteritis or irritable bowel because nobody asked the right question.
Report your illness to your local or state health department. It is not bureaucracy for its own sake — patient interviews are, in this outbreak, the primary evidence. The 90 per cent figure that pinned this on iceberg lettuce came from people answering questions about what they had eaten.
Keep your records if you were seriously affected: positive test results, medical notes, receipts, loyalty-app purchase histories, and a written list of everywhere you ate in the two weeks before symptoms began. Naming Taylor Farms as the supplier the traceback converged on does not by itself clear the restaurants and retailers that served or sold the lettuce.
And do not assume a summer stomach bug automatically belongs to this outbreak. The CDC has been investigating several unrelated Cyclospora clusters at the same time — North Carolina's parsley and cilantro cluster among them — and at one point in late July, six separate Cyclospora investigations were open on the FDA's table simultaneously. A laboratory test is what connects an individual case to a source.
THE UNCOMFORTABLE LESSON
Every large produce outbreak eventually raises the same question: how did this get through?
Cyclospora arrives on fresh produce through contaminated water and poor sanitation somewhere in the growing chain. It cannot be washed off at the processing plant, cannot be killed by refrigeration, and cannot be detected reliably at the border. Screening was increased. It found nothing — which, given what we now know about the organism, was almost predictable.
That leaves prevention entirely upstream, in irrigation water and field sanitation thousands of miles from the person eating the salad. The FDA's inspections at the growers and the Mexican processing facility, still ongoing, are the part of this story that actually matters for next summer.
The CDC also notes that this single outbreak was a major driver of a sharp national increase in Cyclospora cases this year — and that more than one contaminated product is usually circulating during the summer season.
Eleven thousand four hundred and fifty-eight confirmed illnesses. Four hundred and ninety-five hospital admissions. Two deaths. Twenty states. Thirty-one states reached by the recall. Sixty-one days of illness onsets, from June 14 to August 15.
And a supply chain in which the most reliable detection method available to modern public health turned out to be asking several hundred sick people what they had for lunch.
