Cyclosporiasis

Cyclosporiasis is a form of food poisoning you get from the parasite Cyclospora cayetanensis (C. cayetanensis or Cyclospora). Symptoms usually start within a week of ingesting the parasite. The main symptom is watery diarrhea. But it can also cause other stomach problems, which may take a long time to go away.

There were over 1,000 cases in the U.S. in 2025. It’s more common in tropical or subtropical parts of the world. It’s also more common in areas that don’t have widespread water treatment. This includes countries in:

• Central America
• South America
• Europe
• Asia
• Africa

A Cyclospora infection can range from mild to severe. You’re at a greater risk of a severe infection if you have a weakened immune system. Children and older adults may also experience severe symptoms.

If you don’t treat it, your symptoms may last a long time. Or your symptoms may go away and come back. It’s not usually life-threatening.

What are the symptoms of cyclosporiasis?

The main symptom is loud, watery (explosive) diarrhea. Other Cyclospora symptoms may include:

• Loss of appetite
• Bloating, including burping and farting
• Extreme tiredness (fatigue)
• Low-grade fever
• Stomach cramps
• Nausea
• Vomiting

In some cases, you may have cyclosporiasis but not have any symptoms.

Cyclosporiasis causes

C. cayetanensis causes cyclosporiasis. It’s a tiny parasite that you can’t see without a microscope. It mostly lives off people and other primates.

How is it transmitted?

Cyclosporiasis spreads through the fecal-oral route — germs from contaminated poop (feces) get into your mouth. This may happen through:

• Contaminated water: This may include drinking untreated water or accidentally swallowing contaminated swimming water (for example, swimming pools, hot tubs or lakes). C. cayetanensis can survive chlorinated pool water for a long time.
• Contaminated foods: There have been links between some kinds of fresh produce and cyclosporiasis outbreaks. It may occur if you use contaminated water to grow or wash produce. Using poop to fertilize produce is also a risk.

There’s no evidence that it spreads from person to person.

What are the risk factors?

Anyone can get cyclosporiasis. But your risk is higher if you live or travel in areas where it’s more common.

Eating fresh, imported produce also increases your risk. There are links between the following fruits and veggies and cyclosporiasis outbreaks in the U.S.:

• Basil
• Cilantro
• Mesclun lettuce
• Raspberries
• Snow peas
• Sweet peas

What are the potential complications?

Cyclosporiasis can make it harder to hydrate properly. Losing a lot of fluids can lead to serious complications, such as:

• Severe dehydration
• Electrolyte imbalance
• Loss of fluid volume in your body

How doctors diagnose cyclosporiasis

A provider will first review your health history, ask about your symptoms and do a physical exam. They may ask you about anything you’ve had to eat or drink recently. They may also ask about any recent travel.

If they think you have cyclosporiasis, they’ll recommend a poop (stool) test. A lab will look for C. cayetanensis in the sample. Some days, you may have a lot of parasites in your poop. But other days, you may not. You may have to give a few samples over several days so your provider can make an accurate diagnosis.

What is the treatment for cyclosporiasis?

Healthcare providers treat it with antibiotics. They usually prescribe trimethoprim/sulfamethoxazole (TMP/SMX) to kill Cyclospora. But they may prescribe ciprofloxacin or nitazoxanide if you have a sulfa drug allergy.

Your provider may also recommend:

• Antidiarrheal medications, like diphenoxylate-atropine or loperamide, to help prevent dehydration and keep important nutrients in your body
• Hydration, which may include water, electrolyte sports drinks or, in severe cases, IV fluids

Will it clear up on its own?

A Cyclospora infection sometimes goes away on its own. But if you don’t treat it, your symptoms may last for a month or longer. This puts you at risk of severe dehydration and other complications. It’s a good idea to check with a healthcare provider to see if you need antibiotics.

Recovery time

With proper diagnosis and treatment, most people feel better after a week or two. But you may still have occasional bouts of diarrhea for up to a month.

When should I see my healthcare provider?

Reach out to a healthcare provider if you have several bouts of watery diarrhea per day. Contact them again if your symptoms come back or get worse after finishing your full course of antibiotics.

Go to the nearest emergency room (ER) if you have a weakened immune system and have any symptoms of infectious disease. You should also go if you have signs of severe dehydration, including confusion, dizziness, dark-colored pee or you’re not peeing as much as you should.

During your appointment, you may want to ask questions like:

• How do I take my medication?
• How can I manage my symptoms at home?
• What should I eat or drink?
• Are there any foods or drinks I should avoid?
• How can I avoid spreading cyclosporiasis?

What can I expect if I have cyclosporiasis?

If you have a healthy immune system, your outlook is good. For some, it’s a self-limiting condition. That means it’ll go away on its own. Antibiotic treatment can help it go away faster.

If you have a weakened immune system, your provider will monitor you closely. Cyclospora can cause severe, ongoing illness if your immune system can’t fight it off.

Is there anything I can do to feel better?

If you have cyclosporiasis, it’s important to stay hydrated and get whatever nutrition you can. Severe diarrhea can cause serious complications. The following can help:

• Get fluids, including water, sports drinks or broth.
• Avoid caffeinated beverages and alcohol.
• Eat food however you can, even if it’s small bites at a time.
• Take all antibiotics as prescribed, even if you’re feeling better.

Can cyclosporiasis be prevented?

You can help avoid it by:

• Washing your hands with soap and water after using the bathroom and before, during and after food prep
• Washing all food prep surfaces, dishes and utensils with hot water and soap after use
• Thoroughly washing or peeling fresh fruits and veggies before eating them
• Avoiding swimming if you have diarrhea, and waiting at least two weeks to swim after it goes away
• Avoiding drinking untreated water or using it to cook