An overview of Colorado tick fever.

Certain features of Colorado tick fever (CTF) virus and the disease it causes may be relevant to studies on bluetongue virus (BTV), or other orbiviruses. Rapid and easy detection of viral antigen in infected tissues and peripheral blood cells by immunofluorescence staining facilitate diagnosis of the disease. The prolonged (3-4 months) viremia is due to persistent intracellular infection, particularly of erythrocytes, in which the virus is protected from antibody or other host defense mechanisms. This results in more efficient maintenance of the virus cycle in nature, but might lead to adverse effects in the human host. Clues to understanding chronic viral infections or viral immunosuppression might be gained by further research on CTF and other orbiviruses.