Cyclosporiasis

• Reporting criteria
• The disease and its epidemiology
• Case definition

• Laboratory testing
• Case investigation
• Disease control measures

• References
• Contact

What and how to report to the Colorado Department of Public Health and Environment (CDPHE) or local public health agency  

• All specimens with a positive test for Cyclospora (regardless of specimen source) should be reported to public health within four (4) days of the positive test result.
  • All positive Cyclospora laboratory tests should be reported to public health, regardless of symptoms. Public health will make the determination of whether the case meets the case definition.
• Cases should be reported using EpiTrax Reportal, fax, or telephone to CDPHE or local health departments (telephone and fax numbers are listed at the end of this document).
• All potential foodborne, waterborne, and enteric disease outbreaks should be reported immediately to CDPHE or local health departments and entered into EpiTrax, even if the causative agent is not yet known.
  • In general, an “outbreak” is defined as an increase in the number of illnesses above what is normally expected among a specific population, within a given area, over a certain period of time.
  • Specifically, a foodborne disease outbreak occurs when two or more people get the same illness from the same contaminated food or drink.

Purpose of surveillance and reporting

• To identify cases for investigation and potential outbreaks
• To monitor trends in disease incidence

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Etiologic agent

Cyclosporiasis, often referred to as “cyclo,” refers to the disease caused by Cyclospora cayetanensis, a coccidian (one-celled protozoan) parasite. Cyclospora infects the cells of the intestinal tract, and infected individuals shed oocysts in their feces. 

Clinical description

Symptoms of cyclosporiasis may vary, but the most common is often watery diarrhea with frequent and sometimes “explosive” bowel movements. Other common symptoms can include loss of appetite, weight loss, increased gas, abdominal cramps and/or bloating, nausea, and fatigue. Less commonly, some patients have reported vomiting, body aches, headache, and a low-grade fever or other “flu-like” symptoms. Some individuals may also experience asymptomatic infection, but these are rare in the United States and most often associated with individuals from endemic countries. If the illness is left untreated, individuals may have symptoms for a month or longer, often with periods of relapsing symptoms. 

Reservoirs

Humans are the only known reservoir for Cyclospora cayetanensis. Research into other species of Cyclospora, have been linked to other animals, including primates. It is believed each species may be host-specific, as no other species of Cyclospora is known to cause human illness. Cyclospora cayetanensis is not endemic to the United States.

Modes of transmission

Cyclospora is spread when someone ingests food or water contaminated with Cyclospora. After someone who is infected with the parasite has a bowel movement, the parasite must sporulate (produce or form spores) outside of the body in the environment, such as the soil, for one to two weeks. When Cyclospora spores contaminate food or water, humans that ingest the food or water are at risk for cyclosporiasis. The parasite is not considered infectious directly after stool is shed due to the lack of time and environment to sporulate. Since the parasite is not infectious directly after being shed, person-to-person spread is unlikely. There is increased risk of transmission for people living or traveling to tropical or subtropical areas where Cyclospora is endemic. 

Incubation period

The average incubation period is seven days but can range from 2 to 14 days or longer.

Infectious period

Cyclosporiasis infections are unlikely to spread directly from person to person.

Epidemiology

During 2023, 264 cases of cyclosporiasis were reported in Colorado, with a five-year average of 114 cases per year (2019-2023). These numbers are influenced by a large 2023 outbreak associated with imported produce served at a Mexican-style retail food establishment.

In 2022, there were 3,091 cyclosporiasis cases reported in the United States, with a five-year average of 3,285 cases per year (2018-2022). Six percent of cases were hospitalized, and less than 1% of cases died. Twenty-seven percent of cases were associated with outbreaks. Additionally, nearly one in five (19%) of cases reported traveling internationally and eating fresh produce during their exposure period. Cyclospora infections follow a seasonal trend, with infections increasing in the early summer and continuing into early fall.

As Cyclospora is not endemic to the United States, the most significant risk factors for cyclosporiasis are international travel to Cyclospora-endemic areas (primarily tropical or subtropical regions) and/or consumption of fresh, imported produce. Outbreaks in the United States have been associated with consumption of fresh, imported basil, cilantro, mesclun lettuce, raspberries, and snow peas. To date, no outbreaks have been linked to commercially frozen or canned produce.

For more data, see Colorado reportable disease data (Colorado data), CDC WONDER (national data), and CDC FoodNet Fast (FoodNet catchment area data).

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Clinical description

An illness of variable severity caused by the protozoan parasite Cyclospora cayetanensis. The most common symptom is watery diarrhea. Other common symptoms include loss of appetite, weight loss, abdominal cramps/bloating, nausea, body aches, and fatigue. Vomiting and low-grade fever also may occur.

Laboratory criteria for diagnosis

• Laboratory-confirmed cyclosporiasis shall be defined as the detection of Cyclospora organisms or DNA in stool, intestinal fluid/aspirate, or intestinal biopsy specimens.

Case classification

Confirmed

• A case that meets the clinical description and at least one of the criteria for laboratory confirmation as described above.

Probable

• A case that meets the clinical description and that is epidemiologically linked to a confirmed case.

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• The Colorado State Public Health Laboratory (“State Lab”) provides testing services to support public health investigations.
• The State Lab may test clinical and/or environmental samples when determined to be necessary for public health investigations. These services vary by pathogen but may include:
  • Testing for individuals who have been restricted or excluded from work or child care by public health
  • Testing for outbreak investigations, with prior approval from CDPHE
  • Other testing services as discussed with CDPHE
• The State Lab maintains a test directory, guidance for submitting samples, and other helpful resources on their webpage.
  • Additional questions can be directed to the Lab Coordinators by email (cdphe_labcoordinators@state.co.us; preferred method) or phone (303-692-3069). 

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Interview all cases of cyclosporiasis, including symptomatic contacts of confirmed cases, to determine:

• Potential source of infection, and implement disease control measures as appropriate
• If others are ill (i.e., could this be an outbreak?) 

Local health departments have primary responsibility for interviews of sporadic cases in their jurisdictions. CDPHE is available to assist with case investigations upon request through FEWWD’s Enteric Disease Interview Team (EDIT).

Forms 

For single cases, use the cyclosporiasis investigation form within the case’s morbidity record in EpiTrax (“Investigation” tab) for the interview, and enter the information into the case’s morbidity record. This cyclosporiasis investigation form includes elements from the Cyclosporiasis National Hypothesis Generating Questionnaire (CNHGQ) and additional fields required by the CDC. The EpiTrax investigation form replaces the REDCap version of the CNHGQ, which was previously used for Cyclospora investigations in Colorado.

If the case reported international travel during their exposure period, even if it was only for one day, you may complete the travel section and subsequently, end the interview. No other additional exposure information needs to be collected. In the travel section, it’s important to document where the case traveled, which fresh foods were consumed at each location, and include hotel/resort names and addresses, where applicable.

If the case did not report international travel, complete the full interview and gather detailed information about each food item consumed. If the case traveled to different counties within Colorado, or to another state, document the travel details and any fresh foods consumed at each location in the travel section.

Determining the exposure period can be difficult for cases who do not have an acute onset of gastrointestinal symptoms. It’s important to do a complete assessment for GI illness, even when the specimen was something other than stool, to determine if any GI symptoms were present, even if mild. Determine the date used to calculate the case’s exposure period as follows:

1. If the case reports diarrhea, then use the onset date of diarrhea to determine exposure period.
2. If the case does not report diarrhea but reports other clinically relevant symptoms, then use the onset date of other symptoms to determine exposure period.
3. If the case does not report onset of any clinically relevant symptoms, then use the specimen collection date to determine exposure period.*

*Do not enter specimen collection date as “onset date” in EpiTrax (clinical tab); use this date to determine exposure period only. “Onset date” in EpiTrax only applies if the case experienced symptoms of illness.

After completing the case interview, enter the information into the case’s morbidity record (CMR) in EpiTrax, including the investigation form, and conduct any necessary disease control activities. If an outbreak is suspected, create a new outbreak in EpiTrax and contact CDPHE, including requests for additional testing at the CDPHE Lab. CDPHE will attempt to prioritize outbreak cases for temporal-genetic-clustering (TGC) at the CDC to determine genetic linkages, as capacity allows. Contact CDPHE immediately if an outbreak is suspected.

Identify and evaluate contacts 

Symptomatic contacts

• Unlike most other enteric illnesses, direct person-to-person transmission is highly unlikely. However, symptomatic contacts of a case should be investigated for shared exposures, including meals.
• Contacts of a confirmed case who have clinically compatible symptoms are epi-linked probable cases and are treated the same as cases with a positive lab test for disease control purposes. See Disease control measures below.
  • Complete a case interview with all epidemiologically linked probable cases.
    • Probable epi-linked cases may also include international travel-associated contacts who shared meals or consumed the same items on the trip.
  • Epi-linked probable cases who have been interviewed should be entered into EpiTrax as a new, probable cyclosporiasis morbidity record (CMR). Link this newly created CMR to the lab-confirmed case’s CMR under the “contacts” tab in EpiTrax.
• Refer symptomatic individuals who have not previously been tested to their health care provider for stool testing and appropriate medical care.
  • Laboratory tests may have a hard time detecting Cyclospora, even when patients have symptoms. Depending on the type of test (e.g., Microscopy), patients may have to submit several stool samples on different days to detect Cyclospora.
• If a common source of infection is suspected (e.g., a shared meal or social event), create an outbreak record in EpiTrax as soon as possible, and contact CDPHE.
  • If the suspected source of infection occurred during international travel, collect the appropriate travel information (e.g., hotel name[s], fresh foods eaten, dates) and document these in the CMR. CDPHE will pass along this information to the CDC for further follow up. 

Reported incidence is higher than usual/outbreak suspected

If the number of reported cases of cyclosporiasis in your jurisdiction is higher than usual, or if an outbreak is suspected, investigate to determine the source of infection. Notify FEWWD as soon as possible to discuss potential stool testing of untested, symptomatic contacts, and enter the outbreak into EpiTrax. CDPHE staff can assist local public health agencies to investigate outbreaks and determine a course of action to prevent further cases, and they can coordinate surveillance of cases that cross county lines.

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Cyclospora (Cyclosporiasis) | CDC

Treatment

Most people with healthy immune systems will eventually recover from cyclosporiasis without treatment. However, if not treated, cyclosporiasis symptoms (including diarrhea) may last from a few days to over a month. People may experience symptoms that “come and go” multiple times during this time frame, making it difficult to pinpoint when symptoms have fully resolved. 

People with weakened immune systems may experience severe or prolonged illness and should contact their health care provider to receive treatment. The illness is typically treated with trimethoprim-sulfamethoxazole antibiotics, often known as Bactrim, Septra, or Cotrim. All of these approved treatments contain sulfa. If a case has a sulfa allergy, they should contact their health care provider for additional treatment options. 

In general, individuals experiencing diarrhea are at risk of dehydration due to loss of fluids. If symptoms persist, worsen, or are severe, cases should promptly seek medical care.

Prophylaxis

No prophylactic treatment of close contacts is recommended.

Education

• Avoid gardening or farming edible foods (such as produce) until diarrhea has resolved.
• Follow food safety handling recommendations for safe preparation and storage, especially for fresh, uncooked produce. However, it is important to know routine chemical disinfection or sanitization of food or water is unlikely to kill Cyclospora:
  • Wash all fresh produce thoroughly under running water before eating, cutting, or cooking the items.
  • Scrub firm fruits or vegetables with a clean produce brush.
  • Even with washing and scrubbing, not all Cyclospora oocysts may be eliminated.
• Avoid food or water contaminated with feces or potentially contaminated water and food in endemic areas.
  • Cooking foods or boiling water is the most effective way to kill Cyclospora.
  • Routine chemical disinfection or sanitization is unlikely to kill Cyclospora.
• Understand the risk of eating ready-to-eat fresh produce in endemic areas.

Managing special situations

Infection with cyclosporiasis is unlikely to be transmitted directly from person to person. In general, once the case’s symptoms resolve (including the resolution of diarrhea for at least 24 hours without the use of anti-diarrheal medications), the case may return to work or school, and no further follow up is necessary.

Refer child care providers and school personnel to the CDPHE Infectious Diseases in Child Care and School Settings for an overview of Cyclospora infections. 

The Colorado Retail Food Establishment Regulations may require additional restrictions or disease control measures for the case, their close contacts, and/or their employer. Consult with environmental health to determine if the case’s place of employment should enact additional disease control measures to be in compliance with the regulations.

Environmental measures

• If an outbreak or cluster is identified, contact CDPHE immediately to discuss further investigation to identify the implicated item and possible environmental sampling.
  • The implicated food item should be removed from the environment following discussions with CDPHE.
• If a commercial food product is suspected, CDPHE Communicable Disease Branch will coordinate follow-up with the CDPHE Division of Environmental Health and Sustainability and relevant outside agencies.
  • Local health departments may be contacted to assist with gathering the implicated food items if testing is able to occur. 

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• FDA Center for Food Safety and Applied Nutrition (CFSAN) detailed food safety recommendations
• CDC’s cyclosporiasis Provider Fact Sheet
• CDPHE’s guidelines for Infectious Diseases in Child Care and School Settings

Almeria S, Cinar HN, Dubey JP. Cyclospora cayetanensis and Cyclosporiasis: An Update. Microorganisms. 2019 Sep 4;7(9):317. doi: 10.3390/microorganisms7090317. PMID: 31487898; PMCID: PMC6780905.

CDC Website: www.cdc.gov (click on “Diseases and Conditions”)

Centers for Disease Control and Prevention (CDC). FoodNet Fast: Pathogen Surveillance Tool. Atlanta, Georgia: U.S. Department of Health and Human Services. Available from URL: http://wwwn.cdc.gov/foodnetfast. Accessed May 27, 2025.

Centers for Disease Control and Prevention. National Notifiable Diseases Surveillance System (NNDSS) Annual Summary Data for years 2016-2022, United States, CDC WONDER online database. Accessed at http://wonder.cdc.gov/nndss-annual-summary.html on May 26, 2025. 

Cyclosporiasis (Cyclospora cayetanensis) 2010 Case Definition | CDC. (n.d.). https://ndc.services.cdc.gov/case-definitions/cyclosporiasis-2010/

Heymann DL, ed. Control of Communicable Diseases Manual, 21st Edition. Washington, DC, American Public Health Association, 2022.

National Notifiable Diseases Surveillance System. Annual Summary Data 2018-2022 Request. (n.d.). https://wonder.cdc.gov/nndss-annual-summary.html

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CDPHE Communicable Disease Branch

• Phone: 303-692-2700 or 800-866-2759
• Fax: 303-782-0338
• After hours: 303-370-9395

CDPHE Lab Coordinators: 

• Email (preferred): cdphe_labcoordinators@state.co.us  
• Phone: 303-692-3069

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