The disease is more common in men and occurs mostly in the summer, but cases can occur year-round. After an incubation period of about 7 days the illness characteristically begins with and abrupt onset of fever lasting about 3 days followed by an afebrile period of variable duration with a relapse of fever and other clinical symptoms. Fever is often accompanied by shaking chills, severe headache, muscle and joint pain, abdominal pain, nausea and vomiting. An itchy bump may develop at the bite but may be absent by the onset of symptoms. A rash may develop in some cases but is not a reliable sign.
Neurologic involvement occurs less often and includes altered sensorium and numbness of extremities.
Left untreated, the primary fever breaks in 3 to 6 days with drenching sweats followed by an afebrile period of about 8 days. Three to five releapses typically occur without treatment. Each succeeding relapse is less severe. Death is rare and limited mainly to infants and the elderly. Just as your body fights off one invader it pops up as another closely related threat.