Cyclosporiasis – Symptoms, Causes, Treatment & Prevention Guide [2026]

Cyclosporiasis is an intestinal infection caused by the parasite Cyclospora cayetanensis. People typically get it by eating contaminated fresh produce or drinking unsafe water, particularly imported fruits, leafy greens, and fresh herbs. The most common sign is watery diarrhea that can persist for a long time. Unlike a typical flu or stomach bug, cyclosporiasis symptoms can come and go over the course of several weeks if left untreated, often improving briefly before returning. This guide covers cyclosporiasis symptoms, how it spreads, treatment options including Bactrim, and how to lower your risk of infection.

What Is Cyclosporiasis?

Cyclosporiasis is a food borne and waterborne illness caused by ingesting microscopic Cyclospora parasite cells, called oocysts, that originate in human feces. Unlike many intestinal infections, the parasite must spend time maturing in the environment — generally one to two weeks under favourable conditions — before it becomes capable of infecting someone new. That’s why cyclosporiasis spreads through contaminated food and water rather than directly between people. In the United States, outbreaks have most often been linked to imported fresh produce, though recent years have also seen cases tied to domestically grown items.

Cyclosporiasis Symptoms

The incubation period for cyclosporiasis averages about one week after exposure, though it can range from as little as two days to two weeks or longer.

Common symptoms of a Cyclospora infection include:

• Watery diarrhea — often frequent and can last for weeks
• Nausea and loss of appetite
• Stomach cramps and bloating
• Fatigue and body aches
• Low-grade fever (less common)

A distinctive feature of this illness is that symptoms often follow a remitting-relapsing pattern — you may start to feel better for a few days, only for diarrhea and other symptoms to return. Weight loss and dehydration can occur in more severe or prolonged cases.

How Is Cyclosporiasis Spread?

Infection happens through ingesting the parasite — it does not spread directly from person to person, since the oocysts need time outside the body to mature before becoming infectious.

Common sources linked to Cyclospora infection include:

• Fresh berries — raspberries, blackberries
• Leafy greens — lettuce, spinach, pre-packaged salad mixes
• Fresh herbs — cilantro, basil, parsley
• Contaminated drinking water or ice

Most U.S. outbreaks have historically been tied to imported produce, though the CDC has also documented domestically acquired cases in recent years.

Cyclosporiasis Treatment

The CDC’s recommended treatment for cyclosporiasis is an antibiotic combination.

First-line treatment: Trimethoprim-sulfamethoxazole (TMP-SMX), sold under brand names including Bactrim and Septra, is the treatment of choice. The standard course for immunocompetent adults is typically 7 to 10 days, and most people start feeling better within a few days of starting treatment.

Without treatment: Otherwise healthy people may eventually recover on their own, but symptoms can persist for weeks — sometimes a month or longer — and often follow a relapsing course. TMP-SMX shortens the illness and helps clear the parasite.

Note: TMP-SMX isn’t suitable for everyone. People with sulfa drug allergies are typically prescribed an alternative such as ciprofloxacin. Pregnant individuals or those with sulfa allergies should talk to a doctor about the best treatment option for their situation.

How to Prevent Cyclosporiasis

You can meaningfully reduce your risk with the following steps:

• Wash produce thoroughly — Rinse all fruits and vegetables under running water, and scrub firm produce.
• Drink safe water — Use treated, bottled, or boiled water when traveling, and avoid ice of unknown origin.
• Practice good hygiene — Wash hands with soap after using the bathroom and before handling food.
• For high-risk groups — Cooking produce is the only reliable way to fully kill Cyclospora, since heat destroys the parasite where routine washing alone may not.

When to See a Doctor

You should contact a healthcare provider if you have watery diarrhea lasting more than a few days, especially if it’s accompanied by signs of dehydration such as reduced urination, dizziness, or dry mouth. Since cyclosporiasis isn’t routinely tested for in standard stool exams, let your provider know if you’ve recently travelled, eaten imported produce, or have had symptoms that keep returning — this helps them know to specifically request Cyclospora testing.

Final Thoughts

Cyclosporiasis can be an uncomfortable and drawn-out illness, but it’s very treatable once correctly diagnosed. The key takeaways are simple: practice careful food and water hygiene, especially with imported produce, and don’t dismiss diarrhea that lingers for more than a few days as “just a bug.” With proper testing and a short course of antibiotics, most people recover fully. For more health and wellness guides like this one, visit Nexus of Nation.