Taco Bell, Lettuce and 'Explosive Diarrhea': The Vegetable-Borne Parasite Behind the Cyclosporiasis Outbreak Explained

A fast-growing cyclosporiasis outbreak has put lettuce, salad greens and select Taco Bell ingredients under scrutiny as thousands of Americans report a parasite-linked illness known for causing severe watery diarrhoea.

Taco Bell has become part of the widening investigation after signs at some Michigan restaurants said the chain was temporarily unable to sell lettuce, cilantro onion, pico de gallo and guacamole because of a nationwide recall. However, public health officials have not confirmed a link to Taco Bell, any specific restaurant, ingredient, supplier or retailer.

A Taco Bell spokesperson said the company removed limited ingredients at select restaurants 'as a precautionary measure' while authorities continue their broader review. That distinction matters. Some people who tested positive reportedly ate at Taco Bell, but others did not, suggesting the outbreak may involve produce distributed across multiple locations rather than a single fast-food chain.

What Is Cyclospora?

Cyclospora cayetanensis is a microscopic parasite that infects the small intestine and causes an illness called cyclosporiasis.

The parasite spreads when people consume food or water contaminated with faecal matter. Fresh produce is a common vehicle because fruits, herbs and vegetables can be contaminated through irrigation water, washing water or handling before they reach consumers.

Cyclospora does not usually spread directly from person to person. After leaving the body, the parasite needs days or weeks in the environment before it becomes infectious, which is why outbreaks often point investigators back towards a shared food source.

Why Lettuce Is Under Suspicion

Michigan has emerged as the centre of the outbreak, reporting more than 3,300 cases, far above the roughly 50 cases the state usually sees in a year. State health officials have said early interviews with patients repeatedly flagged lettuce and salad greens as possible sources. The CDC and FDA are also investigating produce items, including lettuce, but no single product has been confirmed as the cause. Past cyclospora outbreaks have been linked to raspberries, basil, cilantro, green onions, snow peas and bagged salad mixes.

The current investigation is complicated by the parasite's long incubation period. Symptoms can take up to two weeks or longer to appear, meaning patients may struggle to remember exactly what they ate.

Symptoms Can Last for Weeks

Cyclosporiasis is rarely life-threatening, but it can be miserable and persistent.

The hallmark symptom is watery diarrhoea, which can be explosive and may come with stomach cramps, bloating, nausea, fatigue, appetite loss, vomiting and low-grade fever. Without treatment, symptoms can last for weeks and may seem to improve before returning.

The CDC has confirmed more than 1,600 domestic cases across dozens of states, with more than 5,100 additional cases under review. No deaths have been reported, though more than 100 people have been hospitalised.

How to Reduce Your Risk

Health officials are not telling Americans to stop eating all fresh produce, but they are urging caution while investigators search for the source.

Wash fruits and vegetables thoroughly under running water before eating, cutting or cooking. For lettuce, Michigan officials recommend buying whole heads, removing the outer leaves and washing the inner leaves yourself rather than relying on pre-washed bagged greens.

Cooking produce is the most reliable way to kill the parasite, but many salad ingredients are eaten raw. That makes careful washing, clean hands and sanitised cutting boards especially important.

Anyone with diarrhoea lasting more than a few days, signs of dehydration or severe fatigue should contact a doctor and ask whether testing for cyclospora is needed.