Federal health officials are racing to pinpoint the source of a growing outbreak of a parasitic illness that has left more than a hundred Americans battling severe, watery diarrhea across nearly a third of the country. The Centers for Disease Control and Prevention says it is investigating clusters of the intestinal disease cyclosporiasis, a condition notorious for producing sudden and unusually forceful diarrhea, sometimes described by doctors and patients alike as “explosive.”
According to the agency’s latest surveillance data, at least 145 cases have been confirmed across 17 states since the outbreak season began on May 1. Twenty of those patients required hospitalization, though no deaths have been reported so far. New York has emerged as the epicenter of the outbreak, recording the largest share of infections, followed by clusters in Illinois and Texas. Other states reporting cases include Alaska, Colorado, Connecticut, Florida, Georgia, Louisiana, Massachusetts, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, and Wisconsin.
Cyclosporiasis is caused by a microscopic parasite known as Cyclospora cayetanensis, which typically spreads when people eat food or drink water contaminated with feces. The illness is far more common among travelers to tropical and subtropical regions, where the parasite thrives; however, investigators say this outbreak appears to be different. Of the confirmed patients, none reported international travel in the two weeks preceding their illness, a detail that has led health officials to conclude the source is almost certainly something contaminated within the United States’ food supply, even though the exact culprit remains unidentified.
The defining symptom of the illness is profuse, watery diarrhea that can strike with little warning and recur even after it appears to subside. Patients frequently describe bouts of diarrhea as sudden and severe, accompanied by cramping, bloating, nausea, fatigue, and, in some cases, vomiting or a low-grade fever. Left untreated, the diarrhea and other symptoms can persist for weeks and, in more stubborn cases, more than a month, cycling between improvement and relapse before finally clearing.
Health officials note that the disease is not usually life-threatening, but the prolonged diarrhea can lead to significant dehydration and weight loss, particularly in young children and older adults. Patients affected by the current outbreak range in age from 5 to 86, with an average age of around 42, and doctors typically treat confirmed infections with a course of antibiotics that can shorten how long the diarrhea and other symptoms last.
Because Cyclospora cannot be spread directly from person to person, investigators are focused squarely on the food supply. Past cyclosporiasis outbreaks in the United States have been traced to imported fresh produce, including cilantro, basil, raspberries, snow peas, and bagged salad mixes. A 2018 outbreak sickened close to 400 people after being linked to salads sold at a major fast-food chain, and a shipment of basil imported from Mexico was blamed for another cluster the following year. Whether a similar product is behind the current wave of diarrhea cases has not yet been determined.
State and federal investigators, including teams from the CDC and the Food and Drug Administration, are interviewing sick patients about what they ate in the days before their symptoms began, hoping to identify a common ingredient or supplier. The CDC has cautioned that the true scope of the outbreak is likely larger than the official case count suggests, since many people who experience mild diarrhea recover on their own without ever being tested for the parasite, meaning their illness goes unreported.
In the meantime, health authorities are urging the public to take basic precautions against foodborne illness: washing hands thoroughly before handling produce, rinsing fruits and vegetables under running water, scrubbing firmer items like melons and cucumbers, and refrigerating cut produce promptly. Anyone experiencing persistent diarrhea, especially if it is watery, frequent, or unusually forceful, is advised to contact a healthcare provider, since a simple stool test can confirm whether Cyclospora is the cause and allow for prompt treatment.
For now, the CDC says its investigation remains active, with public health teams in multiple states working to trace the outbreak back to its source before case numbers, and the toll of diarrhea-related illness, climb any further.
