Cyclosporiasis

Cyclosporiasis is caused by a tiny one-celled parasite called Cyclospora cayetanensis (C. cayetanensis). The Cyclospora oocysts are passed in the stool (feces) of an infected person. Oocysts are the hard-shelled young life stage of the parasite that are shed in the feces. The disease spreads when a person consumes food or water exposed to human feces containing Cyclospora.

Once passed in stool, Cyclospora oocysts need time outside the body to become infectious. They stay and mature in the environment for 1 to 2 weeks before they can infect another person. Because of this time lag, the illness is unlikely to spread from person-to-person.

C. cayetanensis only affects humans. Animals cannot be infected or spread the illness.

In the United States, cyclosporiasis outbreaks mostly occur during the spring and summer months. These outbreaks have been linked to contaminated fresh produce, including:

• Lettuce and other leafy greens, including bagged lettuce and salad kits
• Cabbage
• Cilantro, basil, and parsley
• Broccoli
• Snow peas and sugar snap peas
• Raspberries

Produce can be contaminated by Cyclospora through:

• Contaminated groundwater or water used for irrigation
• Sewage spills or leaks
• Poor worker hygiene

In some parts of the world, cyclosporiasis is always present in the environment (endemic). This is likely due to poor sanitation and contaminated food, water, and soil. Endemic cyclosporiasis is more common in tropical or subtropical countries.

Cyclosporiasis symptoms usually begin about 1 week after infection. However, symptoms can start as early as 2 days or as late as 2 weeks after infection. Some people have no symptoms. This is more common in areas where the illness is endemic.

Symptoms include:

• Watery diarrhea (may be explosive)
• Frequent bowel movements (up to 6 times a day)
• Stomach cramps
• Abdominal gas and bloating
• Nausea
• Loss of appetite
• Weight loss
• Fatigue
• Body aches
• Vomiting
• Low fever

Some people are more likely to experience severe symptoms:

• People with a weakened immune system
• Older adults
• Young children

If left untreated, symptoms may come and go and last a long time.

Your health care provider will perform a physical exam and ask about your symptoms.

Your provider may ask about:

• Foods and drinks you have consumed within the last week or two
• Any recent travel to areas where Cyclospora may be present

If your provider thinks that you have cyclosporiasis, you’ll be asked to provide a stool sample. Routine stool tests cannot detect Cyclospora. Your provider will order special laboratory tests to find the parasite. These tests may include special stains or a molecular test called polymerase chain reaction (PCR). If you think you may have cyclosporiasis, ask your provider about testing specifically for Cyclospora.

The parasite is not always found in every stool sample. So, you may need to give more than one sample over several days. Stool samples must be collected before you take any anti-diarrhea medicines or antibiotics. These medicines can interfere with the test.

The goal of treatment is to stop the infection and control symptoms. Your provider will prescribe an antibiotic called trimethoprim-sulfamethoxazole (TMP-SMX). This medicine kills the parasite and helps relieve symptoms. If you are allergic to sulfa drugs, you may be given ciprofloxacin or nitazoxanide instead. However, these medicines do not work as well as TMP-SMX.

Treatment to manage diarrhea and prevent dehydration may include:

• Anti-diarrheal medicines such as diphenoxylate-atropine or loperamide. DO NOT use these medicines without talking to your provider if you have bloody diarrhea, a fever, or the diarrhea is severe. Do not give these medicines to children.
• Rehydration or electrolyte drinks to replace fluids and minerals lost from diarrhea.
• Fluids given through a vein (IV), if you have diarrhea, and you can’t drink or keep down fluids. This may be more common in young children.
• Get plenty of rest while your body recovers from the illness.

If you take diuretics ("water pills") or ACE inhibitors for high blood pressure, ask your provider if you need to stop taking the medicine while you have diarrhea. Never stop or change medicines before talking to your provider.

Most people start to feel better within a few days after starting treatment. Be sure you take all of the medicine as prescribed, even if you start to feel better. If you don’t take all of your medicine, the illness may come back.

Without treatment, the illness can last weeks to months and may return even after symptoms have improved.

You can get infected with Cyclospora more than once in your lifetime.

People with weakened immune systems may have complications and take longer to recover. However, cyclosporiasis is usually not life-threatening.

Complications may include:

• Severe dehydration that may lead to hospitalization
• Significant weight loss
• Poor nutrition or malabsorption due to prolonged diarrhea
• Severe illness in people with weak immunity

In rare cases, the following complications can occur:

• Cholecystitis (infection of gallbladder)
• Reactive arthritis

Contact your provider if you have:

• Several bouts of watery diarrhea a day that doesn’t go away
• Signs of dehydration such as dry mouth, dizziness, less urine, or extreme thirst
• Severe stomach pain
• A weakened immune system and new diarrhea symptoms
• Symptoms that do not improve with treatment

There is no proven way to completely remove or kill Cyclospora on fresh produce. Thoroughly washing produce, even with a sanitizing solution, will not remove it completely.

Safe food habits to help prevent food poisoning can help lower your risk of having a Cyclospora infection:

• Wash and peel fresh fruits and vegetables before consuming them. Wash fresh produce under running water. Do not use soap or bleach.
• Remove the outer layers of produce, such as the first 2 to 3 layers of leafy greens, before consuming.
• Wash your hands with soap and water after using the bathroom, changing diapers, and before preparing or eating food.
• Cook produce to a temperature of at least 158°F (70°C). This will kill the parasite.
• Avoid food from places where it may have been prepared or handled under unsanitary conditions.
• Use safe drinking water, especially while traveling.
• Follow food safety alerts and food recalls from public health agencies.

There is no vaccine available to prevent cyclosporiasis.

Cyclospora infection; Cyclospora enteritis

Centers for Disease Control and Prevention website. About cyclosporiasis. www.cdc.gov/cyclosporiasis/about/index.html. Updated July 27, 2026. Accessed July 30, 2026.

Centers for Disease Control and Prevention website. Preventing cyclosporiasis. www.cdc.gov/cyclosporiasis/prevention/index.html. Updated July 27, 2026. Accessed July 30, 2026.

Corrales-Medina VF, Bogoch II, Suh KN. Cyclospora cayetanensis, Cystoisospora belli, Sarcocystis Species, Balantidium coli, and Blastocystis Species. In: Blaser MJ, Cohen JI, Holland SM, et al, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 10th ed. Philadelphia, PA: Elsevier; 2026:chap 289.

HealthyChildren.org website. Cyclosporiasis in children: symptoms, treatment & prevention. www.healthychildren.org/English/health-issues/conditions/infections/Pages/cyclosporiasis-in-children-symptoms-treatment-and-prevention.aspx. Updated July 28, 2026. Accessed July 30, 2026.

Iordanov R, Serpa JA. Cyclosporiasis, cystoisosporiasis, and microsporidiosis. In: Cherry JD, Kaplan SL, Harrison GJ, Steinbach WJ, Hotez PJ, Williams JV, eds. Feigin and Cherry's Textbook of Pediatric Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2025:chap 234X.

JAMA Network website. What Is cyclosporiasis? jamanetwork.com/journals/jama/fullarticle/2852106. Updated July 21, 2026. Accessed July 30, 2026.

US Food and Drug Administration. Cyclosporiasis and fresh produce. www.fda.gov/food/foodborne-pathogens/cyclosporiasis-and-fresh-produce#Fresh. Updated November 18, 2022. Accessed July 30, 2026.

US Food and Drug Administration. Cyclospora. www.fda.gov/food/foodborne-pathogens/cyclospora. Updated July 16, 2026. Accessed July 30, 2026.

Updated by: Jatin M. Vyas, MD, PhD, Roy and Diana Vagelos Professor in Medicine, Columbia University Vagelos College of Physicians and Surgeons, Division of Infectious Diseases, Department of Medicine, New York, NY. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.