Dr. Herbert Dupont, is a world recognized expert on infectious diarrhea. He has been on the faculty of both Baylor University and the McGovern School of Medicine in Houston. He has been a member of the Texas Club of Internists (now the Texas Society of Medicine) and has lectured to our group on a number of occasions over the years. He was speaking to us about traveler’s diarrhea which he had studied for years. Many of the studies were done on American medical students studying in Guadalajara. I asked him what he did for produce that he brought into his house. He replied, “Everything that comes into the house gets a shower and a bath.” I was pleased that when he lectured again to our group some years later, he incorporated his response into his lecture. It was good advice then and it holds true now. Here is some information on cyclosporiasis which has been in the news lately.
Cyclosporiasis is an infection of the small bowel caused by the parasite Cyclospora cayetanensis.
People are infected after eating food or drinking a liquid that is contaminated with Cyclospora oocysts, which are microscopic, thick-walled forms of the organism released into human stool by people infected with Cyclospora. The most common foods associated with cyclosporiasis infection are fresh produce with ridges or crevices that are difficult to clean and are eaten raw, such as raspberries, leafy greens, and herbs. Cyclosporiasis is not transmitted directly from person to person.
The most common symptom of cyclosporiasis is watery diarrhea with frequent bowel movements, sometimes described as “explosive,” which occurs between 2 and 12 days after ingestion of Cyclospora oocysts. Other common symptoms include loss of appetite, abdominal cramping or bloating, weight loss, increased flatulence, and fatigue. Without treatment, symptoms of cyclosporiasis may last for weeks to months; some people may initially improve and then have recurrence of symptoms.
Outbreaks of cyclosporiasis can occur when large amounts of produce are contaminated either during harvesting or processing. Because food is shipped all over the world, many people in different geographic areas can develop cyclosporiasis from a common source. Prior large outbreaks of cyclosporiasis have been linked to contaminated romaine lettuce, sugar snap peas, raspberries, and fresh herbs such as cilantro and basil. In mid-June 2026, a cyclosporiasis outbreak was first identified in the US; as of July 17, based on data from the US Centers for Disease Control and Prevention (CDC), there were 1645 confirmed cases of cyclosporiasis and more than 5100 additional suspected cases in 34 states. However, the actual number of infections is likely substantially higher because some people have mild symptoms and many do not seek medical care. On July 16, the CDC announced that an outbreak of cyclosporiasis in 5 states was linked to shredded iceberg lettuce; the CDC is currently also investigating several other outbreaks of cyclosporiasis in the US that may have a different source.
Cyclosporiasis is diagnosed when examination of a stool sample under a microscope reveals oocysts or when a laboratory technique called polymerase chain reaction (PCR) identifies C cayetanensis DNA. Because oocysts can be difficult to detect, sometimes multiple stool samples may need to be examined to identify them and make the diagnosis of cyclosporiasis. Individuals with cyclosporiasis are usually treated with an antibiotic (trimethoprim-sulfamethoxazole) for 7 to 10 days, which typically reduces symptoms of diarrhea within several days. Patients with a weakened immune system may need to take antibiotics for a longer period. Patients with cyclosporiasis should also drink fluids to avoid dehydration from diarrhea.
The best way to prevent cyclosporiasis is to avoid contaminated food or drink. Cyclospora oocysts are inactivated by heat, so food that is cooked is considered safe. Freezing produce reduces the risk of cyclosporiasis but does not eliminate it entirely. People should wash raw produce thoroughly in running water before eating it. Removing the outer layer of produce (such as with a head of lettuce) decreases risk of cyclosporiasis because oocysts are usually found on the outer parts of produce. Additionally, people should wash packaged produce (such as salad mixes) even if the label states that it was prewashed.
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