NEW YORK — Infections from the diarrhea-causing parasite cyclospora are surging, with state-level data suggesting that 2026 is already the nation’s worst year for reported cases.
More than 30 states have reported infections this year, and current data from them shows the number of infections surpassing the record U.S. mark of about 4,700 set in 2019. The illness is not usually life threatening and is typically treated with antibiotics.
Health officials have not yet definitively identified what is causing the infections. But in Michigan — where more than 3,300 cases have been reported — officials say early information points to lettuce or salad greens as a possible culprit.
After conducting more than 1,000 interviews with patients, “early information has shown lettuce as a common product that regularly comes up during the investigation,” said Natasha Bagdasarian, the Michigan health department’s chief medical executive.
Because of that commonality and because produce has been behind some past cyclospora outbreaks, Michigan officials advised consumers to buy whole heads of lettuce, discard the outer layers and thoroughly wash what’s left. They also suggested people avoid bagged lettuce and pre-mixed salad kits.
On Tuesday, the Taco Bell restaurant chain issued a statement saying it had “voluntarily and temporarily removed limited ingredients at select restaurants as a precautionary measure. We will continue to closely monitor the situation and follow the guidance of public health authorities.”
Cyclospora is a microscopic, spherical parasite that commonly causes watery diarrhea “with frequent and sometimes explosive bowel movements,” according to the U.S. Centers for Disease Control and Prevention. Outbreaks tend to occur most often in the late spring and summer.
The heat-loving parasite infects the bowels and spreads through feces. In the past, people have been infected by consuming fruits or vegetables that were exposed to feces-contaminated irrigation water.
The illness, called cyclosporiasis, is less common than foodborne illnesses caused by other germs, including salmonella and E. coli. Many cases are never linked to a specific food or other source and, for years, few U.S. cyclospora outbreaks were reported. But the number started rising about a decade ago, with a particularly notable spike in 2018 and 2019.
Experts say it’s likely that cyclospora cases historically were underreported, in part because some common tests used to check for food poisoning have not been geared to detect cyclospora. They attribute the increasing trend in cases to climate change and better detection.
The worst year in the U.S. for infections was 2019, when about 4,700 illnesses were reported, according to federal data on confirmed and suspected cases.
The Centers for Disease Control and Prevention keeps those numbers, but they traditionally lag what’s posted by individual city and state health departments dealing with local outbreaks in real time. On Tuesday, CDC officials issued a health alert that said that since May 1, the agency is aware of 1,645 confirmed domestic cases and more than 5,100 that require further analysis to confirm whether the infections were acquired in the U.S. The reports come from 34 states, the CDC said.
The federal alert did not detail how many reports came from each state. But Michigan officials have reported more than 3,300 cases, officials in northwest Ohio said they have seen more than 1,100, New York City officials counted more than 400, and Illinois reported more than 200.
Officials do not think all can be tied to a common source. In Illinois, for example, more than half the people with infections said they had travel outside the United States, and at least some may have been infected elsewhere.
But Michigan officials believe a large share of their total is likely due to a linked domestic outbreak.
