ATLANTA—U.S. health officials said cases of cyclosporiasis continue to rise across the country as investigators work to identify the source of a growing outbreak linked to the Cyclospora parasite, with authorities warning that additional infections are likely to be reported through the summer.
The U.S. Centers for Disease Control and Prevention (CDC) said laboratory-confirmed cases have spread across 34 states, while thousands of additional reports remain under investigation because of delays in testing and reporting. Officials said the current surge represents one of the largest seasonal increases in recent years and expect case counts to continue climbing through at least the end of August as surveillance continues.
Michigan has emerged as the hardest-hit state, reporting more than 3,300 cases, with health officials also identifying substantial outbreaks in neighboring Midwestern states. Federal investigators said epidemiological evidence suggests some of the outbreaks may be connected, although they have not confirmed a single source of contamination.
Cyclospora cayetanensis is a microscopic parasite that causes an intestinal illness known as cyclosporiasis. According to the CDC, people typically become infected after consuming food or water contaminated with the parasite, most commonly fresh produce. Symptoms include watery diarrhea, stomach cramps, nausea, fatigue, loss of appetite and, in some cases, prolonged illness lasting several weeks if left untreated.
During a public briefing this week, CDC officials said identifying the source has proven difficult because symptoms often begin one to two weeks after exposure, making it challenging for patients to accurately recall foods they consumed. The agency said it is combining patient interviews, laboratory genotyping and food traceback investigations with the U.S. Food and Drug Administration to determine whether contaminated produce is responsible. Officials stressed that no specific food item has yet been confirmed as the source of the multistate outbreak.
State investigators, particularly in Michigan, are examining lettuce and other salad ingredients as possible vehicles of infection. Some food retailers and restaurant chains have voluntarily removed certain produce items while the investigation continues, although health authorities have not established a definitive link between those products and the outbreak.
The CDC said confirmed case totals likely understate the true scale of the outbreak because of reporting delays and ongoing laboratory analysis. Health officials advised consumers to follow food safety guidance, noting that while washing produce may reduce some contamination, cooking remains the most effective way to eliminate the parasite from food. Federal and state agencies said they will continue updating the public as additional epidemiological and traceback evidence becomes available.
