Colorado Tick Fever is a rare viral disease transmitted by ticks that commonly inhabit the western United States. Major symptoms may include fever, headaches, muscle aches, and/or generalized discomfort (myalgia). The symptoms usually last for about a week and resolve on their own.
Colorado Tick Fever typically has a sudden onset about five days after a tick bite. It usually occurs at moderate altitudes during spring or early summer. The symptoms are flu-like and may include chills, headache, increased sensitivity to light (photophobia), fatigue, nausea, vomiting, and a lack of appetite. Muscle pain occurs, especially in the legs and back. There may be a slight, reddish rash, and the spleen can become enlarged (splenomegaly). Fever may rise sharply for two or three days and then subside only to return after a day or two (biphasic fever). The second fever typically subsides after 2 to 4 days.
In very rare childhood cases, severe illness involving the central nervous system may occur. Symptoms may include acute inflammation of the membranes around the brain (aseptic meningitis) and/or spinal cord (encephalitis).
Colorado Tick Fever is a rare viral disease caused by a virus belonging to the Coltivirus family. It is transmitted to humans through the bite of the wood tick (Dermacentor andersoni).
Colorado Tick Fever is a rare viral disease that affects males and females in equal numbers. Most reported cases have occurred in the Rocky Mountain area of the United States and the western provinces of Canada. Several hundred cases of this disease are reported each year in these areas where the wood tick lives (endemic). However, it is possible that many additional cases are misdiagnosed or undiagnosed.
The diagnosis of Colorado Tick Fever is confirmed by isolation of the virus from the blood. Treatment for Colorado Tick Fever is symptomatic and may include acetaminophen to relieve headaches and muscle pain.
The most effective means of preventing Colorado Tick Fever is the use of protective clothing or chemical tick repellents when visiting endemic areas during the spring and summer. Individuals should inspect themselves frequently for ticks and quickly remove them when found.
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Attoui H, et al., Serologic and molecular diagnosis of Colorado tick fever viral infections. Am J Trop Med Hyg. 1998;59:763-68.
Attoui H, et al., Complete nucleotide sequence of Colorado tick fever virus segments M6, S1 and S2. J Gen Virol. 1997;78:2895-99.
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