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NAME: Colorado Tick Fever Virus

SYNONYM OR CROSS REFERENCE: Colorado tick fever (CTF), mountain fever and mountain tick fever Footnote 1, Footnote 2, tick-borne fever Footnote 3, and arbovirus.

CHARACTERISTICS: Colorado tick fever virus (CTFV) is a member of the genus Coltivirus and family Reoviridae Footnote 1. The virus is a non-enveloped virus, 80 nm in diameter, with two outer capsid shells and a double-stranded RNA genome Footnote 2. It is also classified as an arbovirus since it is transmitted by insects Footnote 4.


PATHOGENICITY/TOXICITY: Colorado Tick Fever Virus (CTFV) is the causative agent of CTF Footnote 1. CTFV causes acute febrile illness, and symptoms can include sudden onset of fever, chills, headache, retro-orbital pain, myalgia, photophobia, and nausea Footnote 2, Footnote 5, Footnote 6. Half of patients have a biphasic fever with a period of recovery followed by a second febrile phase Footnote 5, Footnote 7. Most patients recover within 2 weeks Footnote 7. Rarely, children develop severe complications, including meningitis, encephalitis, and hemorrhagic disease Footnote 3, Footnote 5. Persistent viremia is characteristic of the disease and virus can be detected for up to 120 days in blood Footnote 7.

EPIDEMIOLOGY: Found in the western North America (i.e. California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, South Dakota, Utah, Washington, Wyoming, Alberta and British Columbia) at elevations between 4 000 and 10 000 feet Footnote 2. The majority of cases occur from May to July Footnote 1, Footnote 2. Approximately 200-400 cases are reported in the US each year Footnote 1, Footnote 7. The approximate male-to-female ratio is 2:1. Most cases occur in persons 20 to 30 years old, although infection has been reported in individuals 2 to 85 years old Footnote 1. Deaths from CTFV are rare Footnote 2.

HOST RANGE: Humans, multiple species of small mammals (e.g. squirrels, chipmunks, porcupine, deer mice and bushy tailed wood rats), and ticks Footnote 2, Footnote 5.


MODE OF TRANSMISSION: Vector-borne (ticks). Ticks acquire the virus by feeding on viremic hosts, and they subsequently transmit the virus in saliva when they feed on a new host Footnote 8. Transmission from blood transfusions has also been reported Footnote 2, Footnote 5.

INCUBATION PERIOD: 0-14 days (although it typically ranges from 3-6 days) Footnote 1, Footnote 2.

COMMUNICABILITY: Not usually transmitted from person-to-person, but transmission of CTFV through blood transfusion has been reported Footnote 2, Footnote 5.


RESERVOIR: Ground squirrels, western chipmunks, wood rats, deer mice Footnote 2, Footnote 5.

ZOONOSIS: Yes – transmitted from animal by tick bites Footnote 3, Footnote 5, Footnote 6.

VECTORS: Ticks, primarily Dermacentor andersoni Footnote 1, Footnote 2; however, other ticks such as D. occidentalis, D. albipictus, D. arumapertus, Haemaphysalis leporispalustris, Otobius lagophilus, Ixodes sculptus, and I. spinipalpus have also been found to be infected with the virus Footnote 2, Footnote 6. An uninfected tick may become infected by feeding on an infected mammalian host Footnote 2.


DRUG SUSCEPTIBILITY: Ribavirin has demonstrated antiviral activity against CTFV in animal models, although its efficacy in humans in unknown Footnote 1.

SUSCEPTIBILITY TO DISINFECTANTS: Partially resistant to lipid solvents Footnote 3. More specific information on CTFV is not available, but viruses belonging to the family Reoviridae have been shown to be susceptible to glutaraldehyde (2%) and accelerated hydrogen peroxide (AHP) (7% (v/v)) Footnote 9.

PHYSICAL INACTIVATION: Completely inactivated by temperature of 60 ºC for 30 min Footnote 10 and acidic conditions (pH 3.0) Footnote 3.

SURVIVAL OUTSIDE HOST: Can survive several days in a serum-saline solution at 37 ºC Footnote 10. Also survives up to 6 weeks in refrigerated blood, and 16-18 months in blood clots Footnote 11


SURVEILLANCE: Monitor for symptoms. Virus can be isolated from blood or detected in erythrocytes using immunofluorescence. ELISA, PCR and Western blot diagnostic tests have also been developed Footnote 5, Footnote 7, Footnote 8.

Note: All diagnostic methods are not necessarily available in all countries.

FIRST AID/TREATMENT: CTF is usually a benign, self-limited disease Footnote 1. No specific antiviral treatment is available, supportive care is the principle treatment Footnote 2. Aspirin should be avoided as it may exacerbate the potential for haemorrhage associated with thrombocytopenia.




LABORATORY-ACQUIRED INFECTIONS: 16 cases of laboratory-acquired infections have been reported up to 1980 Footnote 12.

SOURCES/SPECIMENS: Blood, cerebrospinal fluid, and tissue from infected humans and animals, and samples from infected ticks Footnote 2, Footnote 6.

PRIMARY HAZARDS: Accidental parenteral inoculation, exposure to infectious aerosols of virus, and bites of infected lab animals and/or arthropods (ticks) Footnote 12.



RISK GROUP CLASSIFICATION: Risk Group 2 Footnote 13.

CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures.

PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes Footnote 14.

OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC). The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities Footnote 14.


SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up Footnote 14, Footnote 15.

DISPOSAL: Decontaminate all wastes that contain or have come in contact with the infectious organism before disposing by autoclave, chemical disinfection, gamma irradiation, or incineration Footnote 14.

STORAGE: The infectious agent should be stored in leak-proof containers that are appropriately labelled Footnote 14.


REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.

UPDATED: February, 2012

PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.

Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.

Copyright ©
Public Health Agency of Canada, 2011


Footnote 1
Klasco, R. (2002). Colorado tick fever. Medical Clinics of North America, 86(2), 435-440.
Footnote 2
Romero, J. R., & Simonsen, K. A. (2008). Powassan Encephalitis and Colorado Tick Fever. Infectious Disease Clinics of North America, 22(3), 545-559.
Footnote 3
Emmons, R. W. (1988). Ecology of Colorado tick fever. Annual Review of Microbiology, 42, 49-64.
Footnote 4
Lanciotti, R. S., & Tsai, T. F. (2007). Arboviruses. In P. R. Murray (Ed.), Manual of Clinical Microbiology (9th ed., pp. 1486-1500). Washington D.C.: ASM Press.
Footnote 5
Kraus, H., Weber, A., Appel, M., Enders, B., Isenberg, H. D., Schiefer, H. G., Slenczka, W., von Graevenitz, A., & Zahner, H. (2003). Viral Zoonoses. In H. Kraus, A. Weber, M. Appel, B. Enders, H. D. Isenberg, H. G. Schiefer, W. Slenczka, A. von Graevenitz & H. Zahner (Eds.), Zoonoses: Infectious Diseases Transmissible from Animals to Humans (3rd ed., pp. 87). Washington, D.C.: ASM Press.
Footnote 6
Brown, R. N., Lane, R. S., & Dennis, D. T. (2005). Geogrphic Distributions of Tick-Borne Diseases and Their Vectors. In J. L. Goodman, D. T. Dennis & D. E. and Sonenshine (Eds.), Tick-Borne Diseases of Humans (pp. 363-391). Washington D.C.: ASM Press.
Footnote 7
Günther, G., & Haglund, M. (2005). Tick-borne encephalopathies: Epidemiology, diagnosis, treatment and prevention. CNS Drugs, 19(12), 1009-1032.
Footnote 8
Wilson, W. R., Sande, M. A., & Drew, W. L. (2001). Current diagnosis & treatment in infectious diseases. New York: Lange Medical Books/McGraw-Hill. Retrieved from
Footnote 9
Howie, R., Alfa, M. J., & Coombs, K. (2008). Survival of enveloped and non-enveloped viruses on surfaces compared with other micro-organisms and impact of suboptimal disinfectant exposure. Journal of Hospital Infection, 69(4), 368-376.
Footnote 10
Trent, D. W., & Scott, L. V. (1966). Colorado tick fever virus in cell culture. II. Physical and chemical properties. Journal of Bacteriology, 91(3), 1282-1288.
Footnote 11
Pantanowitz, L., Telford III, S. R., & Cannon, M. E. (2002). Tick-borne diseases in transfusion medicine. Transfusion Medicine, 12(2), 85-106.
Footnote 12
Scherer, W. F., Eddy, G. A., & Monath, T. P. (1980). Laboratory safety for arboviruses and certain other viruses of vertebrates. American Journal of Tropical Medicine and Hygiene, 29(6), 1359-1381.
Footnote 13
Human Pathogens and Toxins Act. S.C. 2009, c. 24. Government of Canada, Second Session, Fortieth Parliament, 57-58 Elizabeth II, 2009, (2009).
Footnote 14
Public Health Agency of Canada. (2004). In Best M., Graham M. L., Leitner R., Ouellette M. and Ugwu K. (Eds.), Laboratory Biosafety Guidelines (3rd ed.). Canada: Public Health Agency of Canada.
Footnote 15
Burnett, L. A. C., Lunn, G., & Coico, R. (2009). Biosafety: Guidelines for working with pathogenic and infectious microorganisms. Current Protocols in Microbiology, (SUPPL. 13), 1A.1.1-1A.1.14.