A fast-growing outbreak of the gastrointestinal parasite cyclosporiasis has infected or is suspected to have infected more than 7,000 people across the United States, with Taco Bell now under investigation as a possible source — though health authorities have not confirmed any definitive link to the chain or any specific ingredient.
Since 1 May, the Centers for Disease Control and Prevention (CDC) has recorded 1,645 confirmed cases, with a further 5,100 under investigation. An additional 440 cases have been identified outside the US. As of 13 July, 141 people had been hospitalised, and cases have spread across 34 to 36 states, depending on the latest counts. Investigators warn the true number of infections is almost certainly far higher.
By the same point last year, the US had recorded just 249 cases of the disease — making the scale of this outbreak deeply alarming to public health officials. The CDC has warned the outbreak is expected to continue well into August.
Michigan at the epicentre of the cyclosporiasis outbreak
Michigan has been the hardest-hit state, recording hundreds of new cases each day. Health officials there have conducted more than 1,000 meal-tracing interviews in an effort to identify the contaminated food source.
"While the investigation is ongoing, current results point to lettuce or salad greens as a potential source for this outbreak, although other food items cannot be completely ruled out," Michigan's health department said in a statement. "No specific type of produce, grower or supplier has been identified as the source."
Michigan's chief medical executive added that investigators want the public to be aware of what has been learned so far so they can take steps to protect their families, noting that lettuce is "a common product that regularly comes up during the investigation."
Some Taco Bell locations in Michigan have posted signs informing customers that lettuce, cilantro, onion, pico de gallo, and guacamole are temporarily unavailable due to a nationwide recall, and that affected menu items will be served without those ingredients.
What Taco Bell and health authorities are saying
Taco Bell has stated it has "voluntarily and temporarily removed limited ingredients at select restaurants as a precautionary measure," while emphasising that public health officials have not confirmed any connection to the chain, any specific ingredient, supplier, restaurant, or retailer.
"The health and safety of our guests is our top priority," the company said, adding that it will continue to be guided by health authorities as the investigation progresses.
While a number of patients interviewed during the investigation had eaten at Taco Bell before falling ill, not all of them had — underscoring that the chain remains one of several avenues being explored rather than a confirmed source.
The CDC has acknowledged significant challenges in tracing the outbreak's origin. Symptoms can appear up to two weeks after infection, by which time patients may have difficulty recalling everything they consumed. Testing fresh produce for the parasite is also technically demanding, requiring large volumes to be washed and the runoff tested — a laborious and imprecise process. Compounding matters, different states use different reporting practices, with some submitting both confirmed and probable cases together, and others waiting until investigations are complete before notifying the CDC.
"We assume a 6-week reporting lag between illness onset and case reporting to CDC; therefore, we anticipate that case counts will continue to rise as data are received," a CDC spokesperson said.
For earlier context on how this outbreak first began to take shape, see our previous coverage of the cyclospora parasite spreading across the US.
What is cyclosporiasis and what are the symptoms?
Cyclosporiasis is caused by Cyclospora cayetanensis, a microscopic parasite that spreads when people consume food or water contaminated with faecal matter — most commonly fresh produce that has not been adequately washed or cooked. It is classified as a "nationally notifiable disease" in the US, meaning every confirmed case must be reported to the government by health officials.
Symptoms typically emerge about one week after infection and can persist for anywhere between a few days and more than a month. The most commonly reported symptom is watery diarrhoea with frequent and sometimes explosive bowel movements. Other symptoms include:
- Nausea and loss of appetite
- Weight loss
- Stomach cramping and bloating
- Increased gas
Less common but reported symptoms include vomiting, body aches, headaches, fever, and flu-like illness. Those affected range in age from two to 95 years old. The disease is rarely fatal, and many people with mild cases recover without medical intervention — a factor that experts say contributes to significant under-reporting.
Gwen Biggerstaff, deputy director of the CDC's division of foodborne, waterborne, and environmental diseases, noted that "the true number of infections is almost certainly higher, because many people with mild illness recover" without seeking medical attention or being formally tested.
Investigators are urging the public to remain vigilant, thoroughly wash all fresh produce, and seek medical advice if symptoms consistent with the illness develop.
