CDC Yellow Book 2024

Travel-Associated Infections & Diseases

Author(s): Anne Straily, Rebecca Chancey

INFECTIOUS AGENT: Cyclospora cayetanensis


Tropical and subtropical regions


Any travelers to endemic regions who consume potentially  contaminated fresh produce


Follow safe food and water precautions


CDC’s Parasitic Diseases Branch, (404-718-4745;
Parasitological diagnosis: DPDx

Infectious Agent

Cyclospora cayetanensis, a coccidian protozoan parasite, causes cyclosporiasis.


Transmission occurs through ingestion of infective Cyclospora oocysts, typically from contaminated food or water.


Cyclosporiasis occurs in many countries around the world, but appears to be most common in tropical and subtropical regions. Outbreaks frequently are seasonal, but seasonality varies in different parts of the world. In Guatemala, detection rates increase during May–August. In Nepal, rates increase during the summer and rainy season (May–October). In Turkey, incidence rates are highest during July–November. No environmental conditions (e.g., temperature, rainfall) have yet been determined to be drivers for the seasonal variation in cyclosporiasis.

People typically become infected through the consumption of contaminated fresh produce or contaminated water. All travelers are at risk of infection, regardless of the purpose or length of their travel in an endemic area; even short-term travelers can become infected. Outbreaks in the United States and Canada typically occur during the spring and summer months; historically these have been linked to consumption of imported fresh produce. No commercially frozen or canned produce has yet been implicated as the source of an outbreak.

During 2011–2015, 415 cyclosporiasis cases were reported among US residents with a history of international travel during their incubation period. The most frequently reported destinations were in the Americas, including Mexico, the Caribbean, Central America, and South America; travel to Africa, Asia, and Europe was reported less frequently among identified case-patients.

Clinical Presentation

The incubation period averages 1 week (range 2 days to ≥2 weeks). Symptom onset often is abrupt, but can be gradual; some people have an influenza- like prodrome. The most common symptom is watery diarrhea, which can be profuse. Other symptoms can include abdominal cramps, anorexia, bloating, body aches, low-grade fever, nausea, vomiting, and weight loss. If untreated, the illness can last for several weeks or months with a remitting–relapsing course.


Cyclosporiasis is diagnosed by detecting Cyclospora oocysts or DNA in stool specimens. Stool examinations for ova and parasites usually do not include methods for detecting Cyclospora unless testing for this parasite is specifically requested. Diagnostic assistance for Cyclospora and other parasitic diseases also is available from the Centers for Disease Control and Prevention; 404-718-4745; Cyclosporiasis is a nationally notifiable disease.


Treatment includes trimethoprim-sulfamethoxazole; no highly effective alternatives have been identified. One case report documented resolution of symptoms after treatment with nitazoxanide in a patient with a sulfa allergy. Anecdotal data suggest that ciprofloxacin is ineffective.


Travelers can reduce their risk for infection by following food and water precautions (see Sec. 2, Ch. 8, Food & Water Precautions), but using chlorine or iodine for water disinfection is unlikely to be effective because oocysts are extremely tolerant of halogens (see Sec. 2, Ch. 9, Water Disinfection).

CDC website:

The following authors contributed to the previous version of this chapter: Barbara L. Herwaldt

Abanyie F, Harvey RR, Harris JR, Wiegand RE, Gaul L, Desvignes-Kendrick M, et al. 2013 multistate outbreaks of Cyclospora cayetanensis infections associated with fresh produce: focus on the Texas investigations. Epidemiol Infect. 2015;143(16):3451–8.

Cama VA, Mathison BA. Infections by intestinal coccidian and Giardia duodenalis. Clin Lab Med. 2015;35(2):423–44.

Casillas S, Hall R, Herwaldt BL. Cyclosporiasis surveillance— United States, 2011–2015. MMWR Surveill Summ. 2019;68(3):1–16.

Hall RL, Jones JL, Herwaldt BL. Surveillance for laboratory-confirmed sporadic cases of cyclosporiasis—United States, 1997–2008. MMWR Surveill Summ. 2011;60(2):1–11.

Herwaldt BL. Cyclospora cayetanensis: a review, focusing on the outbreaks of cyclosporiasis in the 1990s. Clin Infect Dis. 2000;31(4):1040–57.

Marques DFP, Alexander CL, Chalmers RM, Chiodini P, Elson R, Freedman J, et al. Cyclosporiasis in travelers returning to the United Kingdom from Mexico in summer 2017: lessons from the recent past to inform the future. Euro Surveill. 2017;22(32):30592.

Ortega YR, Sanchez R. Update on Cyclospora cayetanensis, a food-borne and waterborne parasite. Clin Microbiol Rev. 2010;23(1):218–34.

Zimmer SM, Schuetz AN, Franco-Paredes C. Efficacy of nitazoxanide for cyclosporiasis in patients with a sulfa allergy. Clin Infect Dis. 2007;44:466–7.