One of the largest foodborne outbreaks in recent years is underway in the United States. Confirmed cases of cyclosporiasis have rapidly increased within a few weeks, and health authorities are still trying to identify the source of the infection, while investigations focus on various fresh produce items. So far, no deaths have been recorded, but hundreds of people have required hospitalization, and the total number of infections is expected to rise due to the time needed for diagnostic confirmation.
A RAPIDLY GROWING OUTBREAK
Since May 1, the Centers for Disease Control and Prevention (CDC) have confirmed 1,645 cases of cyclosporiasis acquired in the United States, spread across 34 states, and are analyzing over 5,100 additional reports that may be linked to the same infection. This is an exceptional increase: during the same period in 2025, only 249 cases were recorded. If the infections still under review are confirmed, the total – writes CNN – will be about 27 times higher than last year’s.
According to the CDC, 141 people have been hospitalized, while no deaths have been reported. “We are seeing an unusually high number of cyclosporiasis cases this season,” said Gwen Biggerstaff, deputy director of the CDC’s Division of Foodborne, Waterborne, and Environmental Diseases, describing the current situation as “a really significant change” compared to previous years.
MICHIGAN, EPICENTER OF THE OUTBREAK
The outbreak is particularly intense in Michigan, where health authorities have recorded over 3,300 cases. Other significant numbers have been reported in Ohio, New York, Kentucky, West Virginia, and numerous other states. The CDC believes that at least 400 infections recorded in Michigan, Ohio, Kentucky, and West Virginia are epidemiologically linked and may have a common source, while other investigations concern independent clusters or cases not yet associated with any outbreak.
According to Biggerstaff, “there are many cases that do not fall within this multistate outbreak and numerous other investigations are ongoing,” confirming an epidemiological picture still evolving.
WHAT IS CYCLOSPORIASIS AND HOW IS IT TRANSMITTED
Cyclosporiasis, explain the CDC, is an intestinal infection caused by the microscopic parasite Cyclospora cayetanensis. The infection is contracted by ingesting food or water contaminated with fecal matter and, unlike many other gastrointestinal infections, it is not normally transmitted from person to person.
Symptoms generally appear between 2 and 14 days after exposure and include watery diarrhea, abdominal cramps, bloating, nausea, loss of appetite, weight loss, and marked fatigue. Without treatment, the illness can last weeks, with a pattern characterized by improvements and relapses. The most frequent complications are related to dehydration, but malabsorption, cholecystitis, and reactive arthritis can also occur.
“If diarrhea persists for more than a couple of days, it is advisable to consult your doctor,” recommends Kawsar Talaat, infectious disease specialist at Johns Hopkins Hospital, who adds: “If diarrhea disappears and then returns, this is another possible sign of a Cyclospora infection.”
WANTED: THE RESPONSIBLE SOURCE
The Food and Drug Administration (FDA) is conducting traceability investigations along the food supply chain to identify the origin of the outbreak. Investigators are reconstructing the foods consumed by infected people in the weeks before symptom onset, an activity made particularly complex by the parasite’s long incubation period, which can be up to two weeks.
In Michigan, over 1,000 patient interviews have indicated lettuce and salad vegetables among the possible foods involved. However, authorities specify that no specific product, grower, supplier, or distributor responsible for the infection has been identified. The FDA also emphasizes that investigations are still ongoing and that, at this time, there are no foods that the public should particularly avoid.
As a precaution, the Taco Bell chain has temporarily removed some ingredients in a limited number of restaurants, while clarifying that health authorities have not established any link between the outbreak and the company.
DIAGNOSIS AND PREVENTION
The CDC has urged doctors to request specific tests when they suspect a Cyclospora infection, as common stool parasite tests may not detect the parasite. In some cases, multiple stool samples are needed to confirm the diagnosis.
The reference treatment, experts say, is trimethoprim-sulfamethoxazole, an antibiotic produced by the German company Eumedica Pharmaceuticals and also marketed as Bactrim, generally administered for 7-10 days. Although many healthy adults recover spontaneously, children, the elderly, and immunocompromised individuals are at higher risk of developing more severe forms of the disease.
Because the parasite adheres to the surface of fresh produce, health authorities recommend thoroughly washing fruits and vegetables under running water before consumption and remind that cooking is the only method that can reliably eliminate Cyclospora from foods.
