Relapsing fever is an infectious disease that can be passed to humans by ticks. Relapsing fever is most common in the western United States.

Symptoms usually start 3 to 11 days (average 6 days) after the tick bite. They may last for several days, go away, and then return (relapse) several days later. Symptoms of relapsing fever include:

• High fever that begins suddenly.
• Headache, often severe.
• Rapid heart rate.
• Muscle aches (myalgia).
• Abdominal pain.
• General feeling of illness (malaise).
• Rash (up to 50% of cases).

Prescription medication is used to treat relapsing fever.