Colorado Tick Fever (CTF) is a tick-borne virus of the genus Coltivirus. CTF is also known as Mountain tick fever, American tick fever, and American Mountain tick fever and was first isolated in human blood in 1944. The virus is most prevalent in March through September, with June seeming to be the month of highest risk for infection. Tick-borne diseases are often associated with the Northeastern United States, but CTF is predominately but not exclusively found in the Western United States and Canada, in very mountainous regions. It is seen most commonly in Colorado, but tick checks and precautions should be made in all states and regions. This is especially relevant to those who camp or engage in other outdoor activities.

Symptoms of CTF usually show themselves within 3 to 6 days after the tick bite, but can appear within up to 20 days. If a tick in these regions has bitten you, watch for the following symptoms: two-staged fever, chills, weakness, sweating, vomiting, nausea, photophobia, rash, muscle pain/aches, and abdominal pain. Complications are rare, but include meningitis and encephalitis. These complications are usually found in children and those with a compromised immune system.

There is no known treatment for CTF, but after fully removing the tick, acetaminophen can be helpful to reduce pain and fever.