Frequently Asked Questions

What is Colorado tick fever?

Colorado tick fever (CTF) is a rare disease that is caused by the CTF virus. CTF virus is spread to people through the bite of an infected tick. The most common symptoms of CTF are fever, chills, headache, body aches, and feeling tired.

How do people get infected with Colorado tick fever virus?

Colorado tick fever virus is transmitted by the bite of an infected Rocky Mountain wood tick (Dermacentor andersoni). It is important to perform tick checks after spending time outdoors and removing ticks before they have a chance to attach. The virus is not spread from person to person, except in rare instances by blood transfusion. Learn more about preventing tick bites here.

Where and when have most cases of Colorado tick fever occurred?

Colorado tick fever (CTF) occurs in people who live in or visit areas of the western United States and western Canada that are 4,000–10,000 feet above sea level. Most cases of CTF occur during spring or summer months when ticks are most active.

Who is at risk for infection with Colorado tick fever virus?

Anyone bitten by a tick in an area where the virus is circulating can get infected with Colorado tick fever virus. People who work outdoors or participate in outdoor activities are most likely to be exposed to ticks.

How soon do people get sick after getting bitten by an infected tick?

The incubation period (time from tick bite to onset of illness) ranges from 1 to 14 days.

What are the symptoms of Colorado tick fever?

The most common symptoms are fever, chills, headache, body aches, and feeling tired. Some patients will have sore throat, vomiting, abdominal pain, skin rash, or stiff neck. About half of all people who develop symptoms of Colorado tick fever virus have several days of fever followed by several days of improvement, then a second short period of fever and illness.

How is Colorado tick fever diagnosed?

Preliminary diagnosis is based on a patient’s symptoms and history of probable exposure to a tick in an area where Colorado tick fever (CTF) occurs. Laboratory tests typically detect CTF virus genetic material (RNA) or antibodies against the virus in blood.

What is the treatment for Colorado tick fever?

There is no specific medication to treat Colorado tick fever. Severe illnesses are treated by supportive care which may include medications to reduce pain and fever, hospitalization, and intravenous fluids.

How can I reduce the chance of getting infected with Colorado tick fever virus?

There is no vaccine to prevent Colorado tick fever (CTF). The best way to prevent CTF is to reduce your risk of tick bites.

  • Use EPA-registered insect repellent
  • Wear long-sleeved shirts and pants
  • Avoid wooded and bushy areas with high grass
  • Perform thorough tick checks as soon as possible after spending time outdoors and remove any attached ticks. Learn how here.

More information about reducing exposure to ticks is available on the CDC Ticks website.

What should I do if I think a family member might have Colorado tick fever?

If you are concerned that someone you know might have CTF, consult a healthcare provider.