Diarrhea is common and often improves within a few days. But when watery diarrhea continues, disappears and then comes back, or occurs after eating contaminated fresh produce, a less familiar infection called cyclosporiasis may be responsible.
Cyclosporiasis is caused by Cyclospora cayetanensis, a microscopic parasite that infects the small intestine. Although it has traditionally been associated with international travel, infections and outbreaks also occur within the United States.
Cyclospora has received increased attention during the 2026 summer season, including an FDA investigation of an outbreak associated with certain shredded iceberg lettuce served at restaurants in several states.
What Is Cyclosporiasis?
Cyclosporiasis is an intestinal infection caused by the parasite Cyclospora cayetanensis.
People become infected when they consume food or water contaminated with the parasite. Fresh produce has been an important source of previous outbreaks.
Foods associated with Cyclospora outbreaks have included:
Leafy greens
Raspberries
Basil
Cilantro
Parsley
Cabbage
Broccoli
Snow peas and sugar snap peas
Cases in the United States tend to increase during the warmer months, particularly from late spring through summer.
Unlike some stomach infections, Cyclospora usually does not spread easily directly from one person to another. After leaving an infected person’s body, the parasite generally needs time in the environment before it becomes capable of infecting another person.
What Are the Symptoms of Cyclosporiasis?
The most characteristic symptom is frequent watery diarrhea.
Other symptoms may include:
Abdominal cramping or discomfort
Bloating
Increased gas
Nausea
Loss of appetite
Unintentional weight loss
Fatigue
Body aches
Headache
Low-grade fever
Occasionally vomiting
Symptoms usually begin about one week after exposure, although the timing can vary.
One feature that can make Cyclospora particularly frustrating is its tendency to linger.
Without treatment, symptoms may last several weeks or longer. A person may even begin feeling better only for the diarrhea and other symptoms to return.
How Is Cyclospora Different From a Typical Stomach Bug?
Many viral gastrointestinal illnesses improve relatively quickly.
Cyclospora deserves consideration when diarrhea is:
Persistently watery
Lasting longer than expected
Associated with significant fatigue or weight loss
Improving and then repeatedly returning
Associated with recent travel
Associated with a known foodborne outbreak or potentially contaminated produce
However, symptoms alone cannot determine whether someone has Cyclospora. Many other infections and gastrointestinal conditions can cause similar symptoms.
How Do Doctors Test for Cyclosporiasis?
Cyclospora can be detected through stool testing.
There is an important catch: testing for Cyclospora may not automatically be included with routine stool testing.
Even some gastrointestinal PCR panels do not test for it.
If a healthcare professional suspects cyclosporiasis, the laboratory may need to be specifically asked to test for Cyclospora.
The parasite may also be shed intermittently and in relatively small amounts. Because of this, a single negative stool sample does not always exclude infection. In some situations, several stool samples collected on different days may be needed.
Can Cyclosporiasis Be Treated?
Yes.
The preferred treatment for cyclosporiasis is the prescription antibiotic combination trimethoprim-sulfamethoxazole (TMP-SMX), commonly known by the brand name Bactrim.
Some otherwise healthy people eventually recover without medication, but untreated illness can last for weeks and symptoms may repeatedly return.
People with weakened immune systems may experience more severe or prolonged illness and may require different treatment considerations.
People who cannot take TMP-SMX because of an allergy or another medical reason should speak with their healthcare professional. There is currently no alternative medication that has been shown to be as reliably effective as TMP-SMX for Cyclospora.
Staying hydrated is also important because prolonged diarrhea can cause significant fluid and electrolyte loss.
Can You Prevent Cyclospora by Washing Produce?
Good food-safety practices can reduce risk, but Cyclospora can be difficult to remove completely from contaminated produce.
The FDA recommends:
Rinsing fresh fruits and vegetables thoroughly under clean running water
Scrubbing firm produce with a clean produce brush
Discarding outer layers of leafy vegetables when appropriate
Washing hands before and after handling food
Keeping cutting boards, utensils and food-preparation surfaces clean
Avoiding cross-contamination between foods
However, washing does not guarantee that Cyclospora will be removed.
The parasite is also resistant to some commonly used chemical sanitizing methods. Produce should not be washed with soap or bleach.
Cooking produce when appropriate provides additional protection because sufficient heat can kill the parasite.
When Should You Seek Medical Care?
Consider contacting a healthcare professional if diarrhea:
Persists for several days
Is unusually frequent or severe
Keeps returning after initially improving
Is associated with significant weight loss
Occurs after possible exposure to a known foodborne outbreak
Occurs after recent international travel
Medical attention is particularly important if you develop signs of dehydration, such as:
Very little urination
Significant dizziness or weakness
Dry mouth
Difficulty keeping fluids down
Fainting or confusion
People who are pregnant, older, immunocompromised, or have significant underlying medical conditions may need evaluation sooner.
What Should You Do Next?
Most episodes of diarrhea are not caused by Cyclospora. But persistent or recurring watery diarrhea should not automatically be dismissed as a routine stomach bug.
If symptoms continue longer than expected, particularly during the spring or summer, after travel, or following a possible foodborne exposure, speak with a healthcare professional. Specific stool testing may be necessary to identify Cyclospora.
Early recognition can help determine the cause of prolonged diarrhea and whether treatment is needed.