Federal health officials are alerting the public to take enhanced precautions with fresh produce due to a spreading parasitic infection known as cyclosporiasis. The Centers for Disease Control and Prevention (CDC) has confirmed over 800 cases in more than half of U.S. states, with an additional 1,500 suspected cases under investigation, indicating the potential for further growth of the outbreak.
In California, between one and 10 cases have been linked to a statewide outbreak as authorities continue to monitor its spread. The illness is caused by the microscopic parasite Cyclospora cayetanensis, which infects the small intestine after consumption of contaminated food or water. Symptoms typically emerge about a week after exposure, though the incubation period can range from two days to over two weeks. Gastroenterologist Dr. Ariel Malamud noted that symptoms often begin five to seven days after exposure.
Cyclosporiasis is characterized by watery diarrhea, often accompanied by frequent and sometimes explosive bowel movements. The parasite spreads when people ingest food or water contaminated with feces. Unlike many common stomach bugs, Cyclospora is unlikely to spread directly from person to person, as it requires at least one to two weeks outside the body to become infectious.
State and federal health officials are investigating multiple outbreaks, but the specific source has not yet been identified. Historically, Cyclospora infections in the U.S. have been associated with fresh produce such as raspberries, basil, cilantro, green onions, snow peas, lettuce, mesclun, and salad mixes. Outbreaks have also been linked to blackberries, watercress, mangoes, and vegetable trays.
Health officials in Michigan, one of the states heavily impacted by the current outbreak, are investigating lettuce or salad greens as potential sources, though the investigation is ongoing. Dr. Bruce Hirsch, an infectious disease expert, commented that the parasite often contaminates healthy and seasonal foods.
To mitigate risk, the CDC recommends thorough handwashing with soap and water before preparing food and after using the restroom, as alcohol-based hand sanitizers do not kill Cyclospora. Commercially frozen produce, cooked foods, and peeled fruits have not been associated with Cyclosporiasis infection to date.
Experts advise careful washing of produce. Dr. Erika Noel, an assistant professor at the University of Hawaii's medical school, suggests separating herb leaves like cilantro and basil while rinsing, and trimming green onions before washing them under running water. While washing produce with a mixture of three parts water and one part vinegar may help, it does not kill the parasite. Re-washing pre-packaged salad mixes or opting for whole heads of lettuce and removing outer leaves are also recommended. Produce with crevices, such as broccoli, cauliflower, and berries, can be more challenging to clean. Noel suggests cooking berries rather than eating them raw during the outbreak.
Thick, soil-covered root vegetables like carrots, potatoes, and radishes require extra cleaning. The CDC also advises peeling fruits and vegetables whenever possible. For melons, scrubbing the rind before cutting is recommended to prevent the knife from transferring contaminants. Cooking produce to an internal temperature of at least 158 degrees Fahrenheit can effectively kill Cyclospora.
While cyclosporiasis is generally not life-threatening, untreated symptoms can persist for weeks or return after subsiding. Individuals with weakened immune systems may experience more severe or prolonged illness. The standard treatment is the antibiotic trimethoprim-sulfamethoxazole. Anyone experiencing persistent diarrhea should seek medical attention, as a special stool test is required for diagnosis. Staying hydrated and resting are important for recovery.