As cyclospora infections in the US enter a new record, Michigan officials are looking at lettuce as a possible cause
Diarrhea-causing cyclospora infections are on the rise in the US, with state-level data suggesting 2026 will be 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 US record of 4,700 set in 2019.
Health officials have not identified what is causing the illnesses.
On Tuesday, health officials said there may be different patterns of infection in different areas, although they believe cases in at least four states – Kentucky, Michigan, Ohio and West Virginia – are linked.
Michigan officials blame lettuce
In Michigan — where more than 3,300 cases have been reported — officials say early data points to lettuce or salad greens as a possible culprit.
After interviewing more than 1,000 patients, “preliminary data showed lettuce as the most common product during the investigation,” said Natasha Bagdasarian, chief executive officer of the Michigan Department of Health.
Because of that similarity and because the produce has been the cause of past cyclospora outbreaks, Michigan officials have advised consumers to buy heads of lettuce, discard the outer layers and thoroughly wash the rest. They also suggest people avoid bagged lettuce and pre-mixed salad kits.
On Tuesday, restaurant company Taco Bell released a statement saying it “voluntarily and temporarily removed limited ingredients from select restaurants as a precautionary measure. We will continue to monitor the situation and follow the guidance of public health authorities.”
In a call with reporters on Tuesday, federal health officials did not directly respond to a question about whether they were targeting Taco Bell or any other food retailer or distributor.
“The FDA is continuing its investigation of the traceability of many products, including the sites reported by patients before they became ill,” said Donald Prater, acting commissioner for food at the US Food and Drug Administration.
Cyclospora can cause ‘explosive’ diarrhea
Cyclospora is a microscopic, round parasite that often causes watery diarrhea that is “frequent and sometimes explosive,” according to the US Centers for Disease Control and Prevention (CDC). Outbreaks are most common in late spring and summer.
The heat-loving parasite enters the intestines and spreads through the feces. In the past, people have been infected by eating fruits or vegetables that were exposed to contaminated irrigation water.
The disease, called cyclosporiasis, is less common than foodborne illnesses caused by other bacteria, including salmonella and E. coli. Most cases have not been linked to a particular food or other source and, over the years, there have been only a few US cyclospora outbreaks. But the number started to rise about a decade ago, with the most notable spike in 2018 and 2019.
Experts say cyclospora cases may have historically been underreported, in part because some of the standard tests used to test for food poisoning were not designed to detect cyclospora. They attribute the increasing trend in conditions to climate change and better detection.
A parasite that causes diarrhea has led to a growing outbreak in the United States that has sickened more than 1,000 people and sent dozens to hospitals. As of Wednesday, several states have reported cases of cyclospora, which can cause watery diarrhea, constipation, fever and nausea. Although cases are common in the spring and summer, the current outbreak has led to an unusually high number, making it one of the largest the country has ever seen. No deaths were reported.
The Public Health Agency of Canada (PHAC) says it is not currently investigating any cyclospora outbreaks in Canada. It says the parasite is rarely found in food and is not in drinking water in Canada.
However, it adds that there is often an increase in cyclospora infections found in Canada linked to eating fresh imported fruits and vegetables in the spring and summer.
Public health in Quebec says it has received 85 reports of cyclospora infections in the province this year, although none appear to be related to the outbreak in the US.
“I think the fact that we haven’t seen any directly related cases means that the food didn’t get into Canada because now it might have been eaten,” said Lawrence Goodridge, director of the Canadian Research Institute for Food Safety at the University of Guelph.
While the risk is low in Canada, he says Canadians traveling anywhere in the US should be careful.
“This outbreak is so spread across the country that Canadians visiting the US, I think, need to be aware,” Goodridge told CBC News.
Symptoms may take days or weeks to appear
The CDC does report infections, but it traditionally delays what is sent to individual city and state health departments dealing with local outbreaks in real time.
On Tuesday, CDC officials issued a health alert saying that as of May 1, the agency is aware of 1,645 confirmed domestic cases and more than 5,100 need further analysis to confirm that the infections were detected in the US
The actual number of cases may be higher than what has been reported so far because some people may have serious illnesses that do not want to be treated, said Gwen Biggerstaff, deputy director of the CDC’s Division of Foodborne, Waterborne, and Environmental Diseases, in a call with reporters.
Cyclospora, a virus that is often spread through fruits and vegetables exposed to contaminated irrigation water, has infected more than 1,000 people and the US Canada’s Public Health Agency says they are investigating any outbreaks.
It can take days to weeks for a person exposed to the parasite to develop symptoms. It is not clear how much people are currently infected or whether multiple exposures have occurred in the past. But Biggerstaff said officials expect case numbers to continue to rise in August.
One outbreak is affecting 4 Midwest states, the CDC believes
The CDC also released information about the investigation into suspected outbreaks linked to Kentucky, Michigan, Ohio and West Virginia, saying more than 400 people have been reported infected since July 13.
But, separately, Michigan officials reported more than 3,300 cases, officials in northwestern Ohio said they saw more than 1,100, New York City officials counted more than 200 and Illinois reported more than 200.
Officials don’t think they can all be tied to the same source. In Illinois, for example, more than half of the infected people say they traveled outside the US, and at least some may have been infected elsewhere.
Michigan officials, however, believe a large portion of their total may be due to a connected domestic outbreak. CDC officials did not go into detail about why they currently think the cases in Michigan, Ohio, Kentucky and West Virginia are part of the same outbreak.
PHAC says Canadians can reduce their risk of getting sick with cyclospora by following safe food handling practices, cooking produce from countries where cyclospora is found, and eating fresh produce grown in Canada, especially during the spring and summer months.
