Health officials are investigating a cyclosporiasis outbreak, a parasitic intestinal illness that has sickened nearly 3,000 people across the U.S. this season, with dozens hospitalized. The uptick, caused mainly by contaminated fresh produce, highlights the seasonal vulnerabilities in the nation’s food supply during peak summer months.
As of July 9, the Centers for Disease Control and Prevention (CDC) has documented 843 confirmed dAs of July 9, the Centers for Disease Control and Prevention (CDC) has reported 843 confirmed domestically acquired cases of cyclosporiasis since May 1. Additionally, the CDC stated that there are over 1,500 more cases currently under investigation. The actual number of cyclosporiasis cases is likely higher than reported, as some individuals recover without seeking medical care and thus are not tested for Cyclospora, according to the CDC.
An NBC News tally of state data puts the broader figure at around 2,912 reported or confirmed cases across more than 30 states. Health officials say 86 people with available information have been hospitalized, but no deaths have been reported.
Michigan has become a hotspot, reporting over 1,000 cases—significantly higher than its usual annual total of around 50. Other states experiencing notable increases include New York, which has reported hundreds of cases, as well as Ohio, Illinois, and Texas. The clusters seem to be linked to fresh produce, although federal investigators have not yet identified a single common source. Several potential clusters associated with restaurants, grocery items, and events are currently under investigation.
In New Mexico, the number of cases climbed from three to nine this year. Health officials said the state is not experiencing a localized outbreak. New Mexico usually reports around eight cases annually. Officials urged residents to practice good food safety habits rather than panic.
‘Explosive’ Symptoms and a Stubborn Parasite
The microscopic parasite Cyclospora cayetanensis causes cyclosporiasis. It spreads through food or water contaminated with human feces. The parasite takes several days to weeks to become infectious after being passed in stool, making person-to-person transmission uncommon. Authorities have mostly traced outbreaks to imported or domestic fresh produce such as cilantro, basil, lettuce, raspberries and snow peas that may have been irrigated or washed with contaminated water.
Fresh farm produce has often been connected to outbreaks. Cyclospora parasites can cling to fruits, vegetables, and herbs, making them hard to wash away.
Dianna Blau, acting chief of the CDC’s Parasitic Disease Branch, said investigating the cyclosporiasis outbreak is difficult because symptoms may take a week or longer to appear. “In an average year, there’s a small proportion of cases that actually get traced back to one particular food item,” she said.
Symptoms can include watery diarrhea, often described as explosive, stomach cramps, bloating, excessive gas, nausea, fatigue, loss of appetite, and low-grade fever. These typically appear about a week after ingestion. In some cases, the illness continues for weeks or months without treatment, leading to dehydration and weight loss. Healthy individuals usually recover with supportive care and, in more severe cases, antibiotics like trimethoprim-sulfamethoxazole.
Challenges in Tracking and Prevention
This year’s outbreak arrives amid changes in federal surveillance. The Department of Health and Human Services has reduced required surveillance to two pathogens: Salmonella and Shiga toxin-producing Escherichia coli (STEC). It made reporting illnesses caused by Campylobacter, Cyclospora, Listeria, Shigella, Vibrio, and Yersinia optional. The changes could have complicated a full national picture even as states like Michigan continue aggressive monitoring.
Investigators face hurdles because produce is widely distributed across state lines, and the parasite’s incubation period can obscure ties between cases. Past outbreaks have been connected to specific farms or suppliers. But pinpointing them often takes weeks. Some chains, including Taco Bell, have removed certain produce items like lettuce, cilantro, guacamole, and onions from menus and have taken precautionary steps.
CDC public health experts recommend thorough washing of all fresh fruits and vegetables under running water. However, this procedure does not always eliminate the risk. They also advised avoiding unpasteurized juices or untreated water. Cooking produce kills the parasite. Travelers to areas with poor sanitation could face a heightened risk.
A Recurring Seasonal Threat
Cyclosporiasis cases typically rise from May through August as warmer weather and fresh produce consumption increase. The U.S. reported about 2,700 cases last year. This season’s numbers are already matching or surpassing that pace in several states.
Federal and state officials continue to coordinate with the Food and Drug Administration (FDA) on traceback efforts. Doctors are being urged to test patients with prolonged diarrhea, particularly those who recently ate raw produce.
