A Cyclospora outbreak linked to shredded iceberg lettuce served at Taco Bell restaurants has sickened more than 1,600 people and hospitalised 94 across Indiana, Kentucky, Michigan, Ohio and West Virginia, prompting an investigation by the US Centers for Disease Control and Prevention (CDC). No deaths have been reported, and no recall had been issued as of July 16..

According to the CDC, illnesses began between May 13 and July 13, 2026. The US Food and Drug Administration (FDA) traced the outbreak to a single supplier of iceberg lettuce from Mexico used by some Taco Bell locations. Not all restaurants in the five affected states received lettuce from that supplier. The FDA has increased border screening of products linked to the investigation.

The Michigan Department of Health and Human Services (MDHHS) analysed food exposure data from 190 people who reported eating at Taco Bell. Of those interviewed, 90% said they had eaten iceberg lettuce, strengthening suspicions that it was the source of the outbreak.

Michigan has recorded the largest number of infections. As of July 13, the state had reported 2,640 cyclosporiasis cases, far above the usual 40 to 50 cases seen annually. Investigators have completed more than 1,000 patient interviews. While lettuce or salad greens appear to be the most likely source, officials said other foods have not yet been ruled out.

Nationwide, the CDC said it had received reports of 1,645 confirmed domestically acquired Cyclospora infections since May 1, along with more than 5,100 additional cases still being analysed to determine whether they were acquired within the United States. This is substantially higher than the 249 cases reported during the same period last year.

Among the 1,645 confirmed patients with available information, 141 (9%) were hospitalised, and no deaths were reported. Cases have been reported from 34 states. Patients ranged in age from 2 to 95 years, with a median age of 44, and 56% were female. All had eaten food in the United States and had not travelled internationally in the two weeks before becoming ill.

The CDC said more than 400 infections reported from Michigan, Ohio, West Virginia and Kentucky appear to be linked through a common source. It added that the actual number of illnesses is likely much higher because many people recover without seeking medical care or being tested. Confirming whether a case belongs to an outbreak can also take up to six weeks, and cyclosporiasis is often underdiagnosed and underreported.

What is Cyclospora?

Cyclospora cayetanensis is a microscopic parasite that causes an intestinal illness known as cytosporiasis. According to the FDA, people become infected after eating contaminated food or drinking contaminated water.

The parasite usually spreads when infected faeces contaminate food or water. Direct person-to-person spread is considered unlikely because the parasite needs several days to weeks outside the body before it becomes infectious.

Symptoms typically begin about a week after infection, although they can appear anywhere from two days to more than two weeks later. The most common symptoms include watery diarrhoea, loss of appetite, weight loss, bloating, nausea and fatigue. Low-grade fever and vomiting occur less frequently.

Without treatment, symptoms may come and go for several days to a month or longer. While the illness is usually not life-threatening, complications can include malabsorption, inflammation of the gallbladder and joint inflammation.

The CDC said routine stool examinations may not reliably detect Cyclospora and advised doctors to specifically request testing if the infection is suspected. Molecular tests should be used where available.

Confirmed infections are generally treated with 7 to 10 days of trimethoprim-sulfamethoxazole for adults and children older than two months, with longer treatment sometimes needed for people with weakened immune systems. Patients are also advised to stay well hydrated.

Food safety advice

The FDA advises consumers to discard the outer two or three leaves of leafy vegetables, rinse produce under running water and avoid relying solely on pre-washed or pre-cut produce, as Cyclospora is resistant to standard chlorine-based sanitisers.

Cooking produce to 70°C (158°F) is considered the most reliable way to kill the parasite because washing alone may not remove it completely.

The CDC similarly recommends washing fresh produce thoroughly under clean running water before eating, noting that chemical sanitisers may not fully eliminate the parasite.

Previous Cyclospora outbreaks in the United States and Canada have been linked to bagged salad mixes, fresh cilantro, basil, raspberries, snow peas and green onions.

The CDC said it is continuing to investigate the source of the wider national outbreak beyond the Taco Bell-linked cases in coordination with the FDA and state health departments. No recall had been announced as of July 16.

Expert explains why outbreaks are detected late

Dr Swati Rajagopal, Senior Consultant in Infectious Disease and Travel Medicine at Aster CMI Hospital, Bengaluru, said Cyclospora outbreaks are often identified late because the infection resembles many other stomach illnesses and doctors do not routinely test for the parasite.

“Standard stool tests may miss Cyclospora unless a special laboratory test is requested,” she said. “It can also take several days or weeks for infected people to seek medical care, provide stool samples and receive laboratory confirmation.”

She said a single contaminated supplier can spread infections across several states because fresh produce is distributed through large supply chains serving supermarkets, restaurants and food service providers over a short period.

“Since Cyclospora cannot be seen, smelled or tasted, contaminated produce is usually eaten without suspicion,” she said, adding that leafy greens are often consumed raw, allowing the parasite to survive.

Dr Rajagopal said tracing an outbreak to a single supplier is generally reliable but requires careful investigation.

“Public health experts combine patient interviews, food purchase records, restaurant invoices, distribution data and laboratory findings to identify the most likely source,” she said. “Conclusions are based on the overall strength of the evidence rather than a single piece of proof.”

She said the gap between the first illnesses and confirmation of an outbreak reflects the time needed for patients to seek care, undergo specialised testing and for health agencies to compare patient histories and trace food supply chains.

According to Dr Rajagopal, faster molecular testing, improved electronic disease reporting, greater awareness among healthcare providers and stronger food traceability systems could help detect future outbreaks sooner.