Tick-borne Relapsing Fever 

What is "relapsing fever"?

Relapsing fever is an infection caused by bacteria called "Borrelia." In Washington and other areas in the western United States, people get relapsing fever through the bite of ticks that feed on rodents. About 2-8 cases of tick-borne relapsing fever (TBRF) are reported each year in Washington State. Most people became infected while vacationing in rural, mountainous areas during the summer months, between May and September.

How is relapsing fever spread to people?

You can only get TBRF if an infected tick bites you. TBRF is not spread from animals or person-to-person. The ticks that transmit TBRF are called "soft ticks" and are different from "hard ticks" that transmit other diseases such as Lyme disease, Rocky Mountain spotted fever, and tick paralysis. Soft ticks are found in the mountains, and live in dark, cool places where rodents nest, such as woodpiles outside buildings, and between walls or beneath floorboards inside. Soft ticks can survive for up to 20 years without feeding and Borrelia bacteria within them can be spread via a bite for over 10 years. Soft ticks prefer to feed on rodents (squirrels, chipmunks, and mice), but may seek out humans if rodents are scarce. Soft ticks usually feed at night, remain attached for only a few minutes, and most people never realize that they were bitten.   

What are the symptoms of TBRF?

Most people who are infected get sick about 8 days (range, 5 to 15 days) after they are bitten by the tick. The symptoms may include a sudden fever, chills, headaches, and muscle or joint aches, and nausea; a rash may also occur. These symptoms continue for 2-9 days, then disappear. This cycle may continue for several weeks if the person is not treated. Untreated TBRF can cause serious complications, especially if infection occurs during pregnancy. Anyone who develops these symptoms should see their health care provider.  

How is relapsing fever diagnosed and treated?

TBRF can be diagnosed by seeing the bacteria on a blood sample under a microscope. TBRF is easily treated with one to two weeks of antibiotics, and most people improve within 24 hours of starting antibiotics. Complications and death due to TBRF are rare.

What can I do to avoid getting relapsing fever?

The most important action you can take is to educate yourself about where and how you are likely to be exposed to TBRF. Be especially aware of the potential risks when visiting or camping in mountain forests. If you're planning to stay in a cabin:

• Check sleeping areas for evidence of rodents—for example, holes in the floor or walls, shredded material from mattresses, and rodent droppings on counters or in cupboards. If you find signs of rodents, follow the cleanup steps listed in the Hantavirus fact sheet. 

• Don't sleep on the floor or on a bed that touches the wall.

• If the dwelling has been unoccupied, change and wash all bedding before use.

How can I control rodents?

Because rodents can pose a risk of other diseases, such as plague and hantavirus pulmonary syndrome, household rodent control should be maintained at all times. In addition to eliminating the rodents in a residence, it is essential to take measures to prevent future reinfestation.

• Thoroughly check the outside walls and foundation of the building for any openings through which rodents might enter.

• Ensure that external doors and windows close with a tight seal.

• Keep all food and garbage in tightly sealed containers. Promptly clean up any leftover or spilled food.

• Avoid feeding squirrels, chipmunks, and other rodents around dwellings. 

• Eliminate woodpiles in or near the house. Store firewood outside, away from walls. Stack wood on pallets or otherwise raised a few inches off the ground; this will discourage rodents form using these areas as nesting sites.

• If you have rodents in your home—get them out! Never approach or handle live mice. Use spring-loaded mousetraps. Wear gloves and spray with bleach and water solution before handling dead mice. If you use poison bait, follow directions carefully.

What can I do for tick control?

Direct control of ticks in an infested building is necessary for comprehensive prevention of TBRF. Eliminating rodents without tick control may actually increase the risk of people becoming infected, because hungry ticks will seek out other mammals to feed on if rodents are unavailable. Contact a licensed professional exterminator to discuss appropriate tick control measures for your dwelling. 

For more information, visit CDC's Relapsing Fever Web page. 

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