Foreign parasite causing explosive diarrhea infiltrates US—with largest outbreak in New York

Federal health officials are investigating a mysterious outbreak of a foodborne parasite that has sickened at least 145 people across 20 states, leaving dozens hospitalized as authorities race to identify the source.

According to the Centers for Disease Control and Prevention (CDC), at least 145 people between the ages of 5 and 86 contracted the parasite cyclospora cayetanensis between May and June 16. Twenty people have been hospitalized, though no deaths have been reported. The outbreak has been reported in 20 states and Washington, DC with New York recording the highest number of cases. Investigators believe contaminated food is behind the outbreak because none of the infected patients reported recent international travel, where the parasite is more commonly found.

"Local, state, and federal (CDC, FDA) public health authorities are investigating several clusters of cases in more than one state," the CDC said. "Investigations to identify potential sources are ongoing." The parasite causes cyclosporiasis, an intestinal illness that typically develops about a week after exposure. Symptoms include severe watery diarrhea, stomach cramps, nausea, vomiting, bloating, fatigue, loss of appetite and low-grade fever. In some cases, patients may not develop symptoms at all.

Without treatment, the illness can persist for weeks or even months, increasing the risk of dehydration. Doctors typically treat the infection with the antibiotic trimethoprim-sulfamethoxazole, commonly sold under the brand names Bactrim and Septra. While cyclospora infections in the United States are often linked to imported fresh produce from tropical and subtropical regions, investigators have not yet identified the food responsible for the current outbreak.

The parasite has previously been linked to cilantro, basil, raspberries, mesclun lettuce, and sweet peas. In 2018, nearly 400 people were infected in an outbreak traced to contaminated McDonald's salads, while imported basil from Mexico was linked to another outbreak in 2019. The CDC warned that the true number of cases is likely higher than the confirmed total, as additional infections may not yet have been diagnosed or reported.