Cryptosporidiosis

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

• 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 Cryptosporidium (regardless of specimen source) should be reported to public health within four (4) days of the positive test result.
  • All positive Cryptosporidium 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

Cryptosporidiosis, often referred to as “Crypto,” refers to disease caused by Cryptosporidium, a coccidian protozoan. C. parvum and C. hominis are the species most often associated with human infection. Cryptosporidium was recognized as a cause of human illness in 1976.

Clinical description

The most common symptom of cryptosporidiosis is profuse, nonbloody, watery diarrhea. Other signs and symptoms include weight loss, stomach cramps, nausea, vomiting, and low-grade fever. Symptoms often wax and wane, but resolve within 30 days in most immunocompetent people (average is 10 days). Immunodeficiency, especially in HIV infection, is associated with an inability to clear the parasite, and the disease may have a prolonged and fulminant clinical course, contributing to death. Asymptomatic infections are common and can serve as a source of infection for others.

Reservoirs

Reservoirs for C. parvum include cattle (especially preweaned calves), humans and other domestic animals. Humans are the primary reservoir for C. hominis.

Modes of transmission

Cryptosporidium is transmitted via the fecal-oral route, through ingestion of contaminated food and water, direct or indirect animal contact, and person-to-person. Waterborne outbreaks from contaminated drinking water and contaminated recreational water (e.g., swimming pools) have been reported, including a drinking water outbreak in Milwaukee that affected 400,000 people in 1993. Zoonotic transmission can occur through contact with feces from infected animals (e.g., veterinarians or children visiting petting zoos). Person-to-person transmission can occur among household contacts, in child care centers and other institutions, and through certain types of sexual contact (e.g., oral-anal contact). Outbreaks have also occurred from eating food contaminated by animal feces (e.g., unpasteurized apple cider). An infected food worker could also be a source of foodborne transmission. 

Infected animals and people excrete large numbers of oocysts in stool. The infectious dose is not certain, but is very low (10 to 30 oocysts). Oocysts are relatively hardy and can survive in the environment for weeks or months. They are resistant to concentrations of chlorine and other disinfectants commonly used for drinking and recreational water treatment. Cryptosporidium can be killed by bringing water to a full, rolling boil or removed by adequate filtration (absolute pore size less than one micron or filters labeled ‘NSF 53’ or ‘NSF 58’ are effective against crypto and other protozoans).

Incubation period

The average incubation period is about 7 days, with a range of 2-10 days.

Infectious period

The disease is communicable for as long as the infected person excretes Cryptosporidium oocysts, which generally begins at the onset of symptoms. Oocysts are excreted in the stool for several weeks after symptoms subside, and they may remain infective outside the body for 2-6 months in a moist environment. As is the case with most enteric illnesses, persons are most infectious when they have diarrhea and are usually more infectious than those who are asymptomatic.

Epidemiology

Cryptosporidium is a leading cause of waterborne disease among humans in the United States, accounting for 50% of waterborne disease outbreaks in 2021. During 2023, 279 cases were reported in Colorado, with a five-year average of 236 cases per year (2019﹘2023). Cases are reported throughout the year, but are more common in the summer and early fall months. Children under five years of age, animal handlers, travelers to endemic areas, men who have sex with men, and close contacts of infected individuals are among those most likely to be infected. 

In 2022, there were 12,606 cryptosporidiosis cases reported in the United States, with a five-year average of 11,183 cases per year (2018﹘2022). Two percent of cases were associated with outbreaks. Between 2017﹘2022, 18% of cryptosporidiosis cases in the FoodNet catchment area were hospitalized and <1% of cases died. Two percent of cases were outbreak-associated, and approximately 10% were acquired internationally.

Between 2009﹘2017, 35% of cryptosporidium outbreaks in the United States were attributed to exposure to pools, cattle (15%), and child care (13%).

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

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Clinical description

A gastrointestinal illness characterized by diarrhea and one or more of the following: diarrhea duration of 72 hours or more, abdominal cramping, vomiting, or anorexia.

Laboratory criteria for diagnosis

Confirmed

• Evidence of Cryptosporidium organisms or DNA in stool, intestinal fluid, tissue samples, biopsy specimens, or other biological samples by certain laboratory methods with a high positive predictive value (PPV); e.g.,
  • Direct fluorescent antibody [DFA] test
  • Polymerase chain reaction [PCR] 
  • Enzyme immunoassay [EIA] 
  • Light microscopy of stained specimen.

Probable

The detection of Cryptosporidium antigen by a screening test method, such as immunochromatographic card/rapid card test; or a laboratory test of unknown method.

Case classification

Confirmed

A case that is diagnosed with Cryptosporidium spp. infection based on laboratory testing using a method listed in the confirmed criteria.

Probable

• A case with supportive laboratory test results for Cryptosporidia spp. infection using a method listed in the probable laboratory criteria. When the diagnostic test method on a laboratory test result for cryptosporidiosis cannot be determined, the case can only be classified as probable OR
• A case that meets the clinical criteria AND is epidemiologically linked to a confirmed case.

Note: Persons who have a diarrheal illness and are epidemiologically linked to a probable case because that individual was only diagnosed with cryptosporidiosis by an immunocard/rapid test/ or unknown test method cannot be classified as probable cases. These epi-links can be considered suspect cases only. Additionally, confirmed or laboratory-confirmed probable cases can include asymptomatic infections and infections at sites other than the gastrointestinal tract that are laboratory-confirmed (rare).

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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 confirmed and probable (including epi-linked probable) cases of cryptosporidiosis to determine:

• Potential source of infection, and implement disease control measures as appropriate 
• If others are ill (i.e., could this be an outbreak?) 
• If the case may be a source of infection for others (e.g., a high-risk worker or a diapered child); and if so, prevent further transmission

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 CDPHE’s Enteric Disease Interview Team (EDIT). Interviews should be conducted and appropriate disease control measures implemented as soon as reasonably possible after the case is reported.

Forms 

For single cases, use the CDPHE Cryptosporidiosis Case Investigation Form for your interview and enter the information into the case’s morbidity record (CMR) in EpiTrax. Interview all cases, regardless of specimen source (stool, intestinal fluid, tissue samples, biopsy specimens, or other biological samples). 

For surveillance purposes, collect exposure histories for the 14 days before symptom onset. 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 collected from a source other than stool, to determine if any GI symptoms were present, even if mild. Use the following criteria to determine the case’s exposure period:

1. If the case reports diarrhea or vomiting, then use the onset date of diarrhea/vomiting to determine exposure period.
2. If the case does not report diarrhea or vomiting but reports other clinically relevant symptoms (see Clinical description section above), 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 (see Clinical description section above), 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. Otherwise, leave this field blank.

If the case reports international travel for even one day during their exposure period, it is fine to complete the travel section then skip to the “School, work, and volunteer information” section. No other additional exposure information needs to be collected.

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 if assistance is needed; this includes requests for additional testing at the State Lab.

Identify and evaluate contacts

Symptomatic contacts

• Contacts of a case with a positive lab test 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.
  • Epi-linked probable cases who have been interviewed should be entered into EpiTrax as a new, probable cryptosporidiosis morbidity record (CMR). Link this newly-created CMR to the laboratory-confirmed case’s CMR under the “contacts” tab in EpiTrax.
• Refer symptomatic individuals who have not previously been tested (especially if they are high-risk workers) to their health care provider for stool testing and appropriate medical care.
• If a common source of exposure is suspected (e.g., a shared meal or social event), please create an outbreak record in EpiTrax and notify CDPHE as soon as possible.  

Asymptomatic contacts 

• Ask about high-risk occupations, including food handling, health care, community residential programs, and child care/school attendance. 
• Provide information on symptom monitoring and next steps if symptoms develop.
  • Stress the importance of good hand washing, personal hygiene, excluding themselves from work, and notifying their supervisor whenever they have a diarrheal illness.  
  • If an asymptomatic contact develops diarrhea, follow the steps outlined above under “Symptomatic contacts”. If the contact works in a high-risk setting, exclude them from work per the Managing special situations section below, even in the absence of a positive lab test.

Reported incidence is higher than usual/outbreak suspected

If the number of reported cases of cryptosporidiosis in your jurisdiction is higher than usual, or if an outbreak is suspected, investigate the situation to determine the source of infection and mode of transmission. Notify CDPHE 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 disease control recommendations to prevent further cases, as well as coordinate surveillance of cases that cross county lines.

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Cryptosporidium ("Crypto") | CDC

Treatment

Immunocompetent persons do not generally require specific treatment; symptoms usually resolve in 2-3 weeks. Nitazoxanide is the only FDA approved treatment for cryptosporidiosis and may be used for immunocompetent patients at least one year old. In people with immunodeficiencies, the illness may be prolonged and may lead to death. Among persons with HIV, antiretroviral therapy can be effective in stopping symptoms and oocyst shedding.

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

Encourage the case to:

• Avoid preparing food for other individuals until diarrhea has resolved. 
• Avoid sex (vaginal, anal, and oral) or use a barrier (condom, dental dam) for two weeks after resolution of diarrhea.
• Avoid swimming for two weeks after resolution of diarrhea (this is due to the low infectious dose and hearty nature of Cryptosporidium oocysts, which are resistant to chlorine).
• Always wash hands thoroughly with soap and water for at least 20 seconds before eating or preparing food, after using the toilet, after changing diapers, and after touching pets or other animals (especially cattle). 
• After changing diapers, wash your hands and the child’s hands for at least 20 seconds. Clean and sanitize diaper changing stations/areas often.
  • In child care and other institutional settings, dispose of stool and soiled diapers/linens in a sanitary manner.
• Avoid drinking untreated water from streams, lakes, rivers, springs, ponds, streams, or shallow wells. Avoid drinking untreated water or ice made from untreated water while traveling in developing countries or whenever the water quality is unknown.
  • Bringing water to a full, rolling boil is sufficient to kill Cryptosporidium or use filters capable of removing particles 0.1 to 1.0 micrometers in diameter. The filter label may read ‘NSF 53’ or ‘NSF 58.’
  • Refer to CDC guidance for effective water treatment options while hiking, camping, and traveling.
• Avoid swallowing water when swimming. Lakes, streams, other surface waters, and swimming pools may be contaminated with Cryptosporidium and chlorination is not effective in eliminating the parasite.
• Adhere to local advisories to boil water. 
• Avoid drinking raw milk, other unpasteurized dairy products, or unpasteurized apple cider. 
• Avoid fecal contact, including sexual practices that may involve direct contact with feces. Latex barrier protection should be emphasized as a way to prevent the spread of Cryptosporidium to case’s sexual partners as well as being a way to prevent the exposure to and transmission of other pathogens.

The likelihood that Cryptosporidium could cause illness in regulated, public drinking water is low. Immunocompromised individuals, however, may want to consider the following recommendations:

• Boil tap water before drinking or making ice cubes.
• Consider the use of a home water filtering system with a very fine filter (absolute pore size of 1 micron or smaller). Such filters include: reverse-osmosis filters; filters labeled as “absolute” 1 micron filters; and those labeled as meeting National Sanitation Foundation (NSF) standard #53 or #58 for cyst removal.

Managing special situations

Food handlers 

• Food handlers must be excluded from work until at least 24 hours after diarrhea has resolved without the use of anti-diarrheal medications and adequate hygiene can be maintained, ideally as verified by environmental health. "Exclude" means to prevent a person from working as an employee in a food establishment or entering a food establishment as an employee. 
  • While individual circumstances may vary, cases are generally not required to provide two consecutive negative stool tests to return to work. 
  • If a case has questionable hygienic practices or there are other concerns, consider excluding the case from work until the case has obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antimicrobials, if antimicrobials are given.
• In an outbreak situation, longer exclusion and/or return to work testing may be required to return to food handling.
• The Colorado Retail Food Establishment Regulations may require additional restrictions or disease control measures for the case, their close contacts, and/or their employer. 
  • Please 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. 

Child care centers/preschools

Refer child care providers to CDPHE Infectious Disease in Child Care and School Settings for an overview of Cryptosporidium infections.

• Children or staff with cryptosporidiosis should be excluded until at least 24 hours after diarrhea has resolved without the use of anti-diarrheal medications. 
  • Parents of cases should be counseled not to take their children to another child care center during this period of exclusion in order to avoid possible transmission of crypto at a new location.
  • Since many child care center staff assist with food preparation and/or feeding children, it is very important that staff with Cryptosporidium infection follow this guidance. See Disease control measures section (Food handlers), above.
  • If there are concerns about hygienic practices at the child care center, consider excluding the case from care until the case has obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antimicrobials, if antimicrobials are given.
  • Parents and staff should be reminded that cases should not swim or wade in pools for at least two weeks after resolution of diarrhea.
• Determine whether additional children or staff are (or have recently been) ill with diarrheal illness.
  • Other children or staff with diarrhea should be excluded and referred to their health care provider for stool testing and appropriate medical care. 
  • If other cases in the center are identified, initiate an outbreak investigation and consider sending a letter home to parents.
    • In an outbreak situation, longer exclusion and/or return to work/child care testing may be required. Contact CDPHE for assistance.
  • If the case is the only person in the classroom or facility who has been ill, no further action is indicated for other children/staff in that classroom or center.
• Reinforce the importance of meticulous hand washing, proper sanitizing and disinfection, and proper diaper changing technique with child care center staff. If possible, this should be verified by environmental health.
• Consult with CDPHE for instances in which children attend drop in style care at gyms, churches, etc.

Schools 

Refer school personnel to the CDPHE Infectious Disease in Child Care and School Settings for an overview of Cryptosporidium infections. 

• Students or staff with cryptosporidiosis  should be excluded until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. 
  • If there are concerns about the case’s hygiene (e.g., the case has developmental disabilities and wears diapers) consider obtaining two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antimicrobials, if antimicrobials are given. before a case returns to school.
• Students or staff who handle food for others must not prepare food until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. See Disease control measures section (Food handlers) above.
• Parents, staff, and students should be reminded that cases should not swim or wade in pools for two weeks after resolution of diarrhea.
• In an outbreak situation, longer exclusion and/or return to work/school testing may be required.

Community residential programs (including facilities serving the developmentally disabled)

Actions taken in response to a case of cryptosporidiosis in a community residential program will depend on the type of program and the level of functioning of the residents. In general: 

• Staff members with cryptosporidiosis  should be excluded from work until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. 
  • For staff members who provide direct patient care (e.g., feed patients, give mouth or denture care, or give medications), follow guidelines for staff in health care facilities below. 
  • While individual circumstances may vary, in general, staff members are not required to provide two negative stool tests to return to work. 
• Residents with cryptosporidiosis  should be placed on contact precautions until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications.
  • If the resident has questionable hygiene, is incontinent, or there are other concerns, the resident should remain on contact precautions until they have obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antimicrobials, if antimicrobials are given. 
• Residents and staff with cryptosporidiosis must be excluded from handling or preparing food for others until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. See Disease control measures section (Food handlers) above.
• Residents and staff should be reminded that cases should not swim or wade in pools for two weeks after resolution of diarrhea.
• In an outbreak situation, longer exclusion and/or return to work testing may be required.

Patients and staff in health care facilities (including hospitals, medical and dental clinics, skilled nursing and long-term care facilities)

Hospitals and skilled nursing/long-term care facilities generally have written infection control policies and procedures for handling cases of communicable disease among patients and staff members. 

If a facility does not have such policies in place, provide the following recommendations: 

• Health care workers with cryptosporidiosis who provide direct patient care or handle medications (e.g. pharmacists) should be excluded from work until at least 24 hours after diarrhea has resolved without the use of anti-diarrheal medications.
  • While individual circumstances may vary, in general, health care workers are not required to provide two negative stool tests to return to work. 
• Patients with cryptosporidiosis  should be placed on contact precautions until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. 
  • If the patient has questionable hygiene, is incontinent, or there are other concerns, the patient should remain on contact precautions until they have obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antimicrobials, if antimicrobials are given.  
• In an outbreak situation, longer exclusion and/or return to work testing may be required.

Environmental measures

• If a private drinking water source is implicated, CDPHE recommends that the owner test for Cryptosporidium and can direct the owner to appropriate commercial laboratories to perform this testing. 
• If a municipal drinking water source or other public supply is implicated, CDPHE will work with the Water Quality Control Division to ensure appropriate testing and follow up. 
• Implicated food items and food prepared by cases must be removed from the environment.
• If a diarrheal event from an infectious case occurred in a swimming pool, the LPHA should work with their environmental health team to implement remediation steps immediately, such as hyperchlorinating the pool. 
• A decision about testing suspect/implicated food items must be made in consultation with CDPHE.
  • The general policy of the State Lab and the Communicable Disease Branch is only to test food samples associated with outbreaks, not in single cases.
• If a commercial product is suspected, CDPHE Communicable Disease Branch will coordinate follow-up with the CDPHE Division of Environmental Health and Sustainability and relevant outside agencies.

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American Academy of Pediatrics. Red Book: 2024-2027 Report of the Committee on Infectious Diseases, 33rd Edition. Illinois, Academy of Pediatrics, 2024.  

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 05/21/2025.
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 22, 2025

Cryptosporidiosis (Cryptosporidium spp.) 2012 Case Definition | CDC. (n.d.). https://ndc.services.cdc.gov/case-definitions/cryptosporidiosis-2012/

Gharpure, R., Perez, A., Miller, A. D., Wikswo, M. E., Silver, R., & Hlavsa, M. C. (2019). Cryptosporidiosis outbreaks — United States, 2009–2017. MMWR Morbidity and Mortality Weekly Report, 68(25), 568–572. https://doi.org/10.15585/mmwr.mm6825a3 

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

Juranek, D. Cryptosporidiosis: Sources of Infection and Guidelines for Prevention. Clinical Infectious Diseases, 1995; 21(supp 1) S57-61.

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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 Laboratory Coordinators

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

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