This disease is limited to the western US and is most prevalent from March to September, with the highest numbers of infections occurring in May and June.

Symptoms start about 3 to 6 days after the tick bite. Symptoms of fever continue for 3 days, stop, then recur 1 to 3 days later for another few days.

Risk factors are recent outdoor activity and recent tick bite. The incidence is high in Colorado, where up to 15% of regular campers show past exposure (based on antibodies). It is much less common in the rest of the US.

• abrupt onset of fever
• sweating, excessive
• severe muscle aches
• joint stiffness
• headache
• photophobia (sensitivity to light)
• nausea and vomiting
• generalized weakness
• occasional faint rash

• blood tests that confirm infection (usually several weeks later)
  • complement fixation to Colorado tick virus
  • immunofluorescence positive for Colorado tick fever
• CBC shows low white blood cell count
• mild increase in liver function tests
• mild increase in creatine phosphokinase

When walking or hiking in tick-infested areas, tuck long pants into socks to protect the legs, and wear shoes and long-sleeved shirts. Ticks will show up on white or light colors better than dark colors, making them easier to remove from your clothing.

Check yourself and your pets frequently. If you find ticks, remove them immediately by using a tweezers, pulling carefully and steadily. Insect repellent may be helpful.