July 2026 Update: Increased cases of cyclosporiasis acquired in the United States have been reported since May 2026 across multiple states, including Ohio. At the time of this update, no source(s) have been identified, however investigations by public health officials are ongoing.
Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cavetanensis. People become infected with cyclosporiasis by ingesting food or water contaminated with the parasite. Once infected, people can shed the parasite in their stool where it matures (becomes infectious) in the environment. Other people may become infected if they ingest any food or water contaminated by the parasite.
Unlike some stomach illnesses, cyclosporiasis does not spread directly from person to person. The parasite must contaminate food or water before causing infection.
Common sources of infection include:
Drinking untreated contaminated water
Accidentally swallowing contaminated water while swimming in pools, hot tubs or lakes
Eating produce fertilized with contaminated stool
Eating fresh produce that was grown or washed with contaminated water
In the United States, outbreaks of cyclosporiasis have been linked to several types of fresh produce, such as herbs, berries and bagged lettuce.
What are the symptoms of cyclosporiasis?
Symptoms usually begin within one week of swallowing the parasite and can last from two days to two weeks. Illness can range from mild to severe, with children and adults who have weakened immune systems at greater risk for more serious illness. Symptoms can mimic those of other more common causes of stomach illnesses:
Watery diarrhea – the most common symptom.
Diarrhea may be prolonged or may return one or more times
Loss of appetite
Abdominal cramping or bloating
Nausea
Fatigue
Low-grade fever
Body aches
Vomiting – less commonly present
How is cyclosporiasis treated?
Most children with healthy immune systems who are infected will recover without treatment. However, symptoms may be prolonged or may return one or more times. Treatment with trimethoprim-sulfamethoxazole, an antibiotic used to treat parasite infections, helps eradicate the parasite.
Children can become dehydrated due to cyclosporiasis, particularly young children, children with severe infection or children with weakened immune systems. Drinking plenty of fluids, such as water, sports drinks or broth, can help prevent dehydration. While recovering, avoid caffeinated beverages and eat, even if it’s only small bites at a time.
Your child’s healthcare provider can help determine whether testing or treatment for cyclosporiasis is needed.
How to prevent cyclosporiasis?
While no prevention method is perfect, these steps can help reduce your family’s risk:
Avoid food or water that is untreated or may be contaminated
Follow safe food handling, preparation and storage practices
Wash your hands with soap and water before and after handling raw produce
Wash produce
Cut away damaged or bruised areas of fruits and vegetables before eating or preparing them
Do not swim if you have diarrhea and wait at least two weeks after symptoms have resolved before returning to the water
When should I call a healthcare provider?
Contact your child’s healthcare provider if they have several episodes of watery diarrhea in a day. You should also reach out if symptoms return or worsen after completing a full course of antibiotics.
Seek emergency care right away if your child has a weakened immune system and develops symptoms of an infectious disease, or if they show signs of severe dehydration, including confusion, dizziness, dark-colored urine or urinating much less than usual.
Matthew C. Washam, MD, MPH, is an assistant professor in the Department of Pediatrics at The Ohio State University College of Medicine and member of the Section of Infectious Diseases at Nationwide Children’s Hospital. Dr. Washam’s research interests include understanding the risk factors for transmission of multidrug-resistant bacteria in children within the hospital environment.
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