Borrelia Burgdorferi (Lyme disease) is the most common vector-borne disease in the United States. Lyme disease is caused by the bacterium Borrelia burgdorferi and rarely, Borrelia mayonii. It is transmitted to humans through the bite of infected blacklegged ticks. Typical symptoms include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. If left untreated, the infection can spread to joints, the heart, and the nervous system. Lyme disease is diagnosed based on symptoms, physical findings (e.g., rash), and the possibility of exposure to infected ticks. Laboratory testing is helpful if used correctly and performed with validated methods. Most cases of Lyme disease can be treated successfully with a few weeks of antibiotics.

Symptoms

The signs and symptoms of Lyme disease vary. They usually appear in stages, but the stages can overlap.

Early signs and symptoms

• Rash. From 3 to 30 days after an infected tick bite, an expanding red area might appear that sometimes clears in the center, forming a bulls-eye pattern. The rash (erythema migrans) expands slowly over days and can spread to 12 inches (30 centimeters) across. It’s typically not itchy or painful but might feel warm to the touch. Erythema migrans is one of the hallmarks of Lyme disease, although not everyone with Lyme disease develops the rash. Some people develop this rash at more than one place on their bodies.
• Other symptoms. Fever, chills, fatigue, body aches, headache, neck stiffness, and swollen lymph nodes can accompany the rash.

Later signs and symptoms

If untreated, new signs and symptoms of Lyme infection might appear in the following weeks to months. These include:

• Erythema migrans. The rash may appear on other areas of your body.
• Joint pain. Bouts of severe joint pain and swelling are especially likely to affect your knees, but the pain can shift from one joint to another.
• Neurological problems. Weeks, months, or even years after infection, you might develop inflammation of the membranes surrounding your brain (meningitis), temporary paralysis of one side of your face (Bell’s palsy), numbness or weakness in your limbs, and impaired muscle movement.

Less common signs and symptoms

Several weeks after infection, some people develop:

• Heart problems, such as an irregular heartbeat
• Eye inflammation
• Liver inflammation (hepatitis)
• Severe fatigue

Prevention

The best way to prevent Lyme disease is to avoid areas where deer ticks live, especially wooded, bushy areas with long grass. You can decrease your risk of getting Lyme disease with some simple precautions:

• Cover up. When in wooded or grassy areas, wear shoes, long pants tucked into your socks, a long-sleeved shirt, a hat, and gloves. Try to stick to trails and avoid walking through low bushes and long grass. Keep your dog on a leash.
• Use insect repellents. Apply insect repellent with a 20% or higher concentration of DEET to your skin. Parents should apply repellant to their children, avoiding their hands, eyes, and mouth. Keep in mind that chemical repellents can be toxic, so follow directions carefully. Apply products with permethrin to clothing or buy pretreated clothing.
• Do your best to tick-proof your yard. Clear brush and leaves where ticks live. Mow your lawn regularly. Stack wood neatly in dry, sunny areas to discourage rodents that carry ticks.
• Check your clothing, yourself, your children, and your pets for ticks. Be especially vigilant after spending time in wooded or grassy areas. Deer ticks are often no bigger than the head of a pin, so you might not discover them unless you search carefully. It’s helpful to shower as soon as you come indoors. Ticks often remain on your skin for hours before attaching themselves. Showering and using a washcloth might remove unattached ticks.
• Don’t assume you’re immune. You can get Lyme disease more than once.
• Remove a tick as soon as possible with tweezers. Gently grasp the tick near its head or mouth. Don’t squeeze or crush the tick, but pull carefully and steadily. Once you’ve removed the entire tick, dispose of it by putting it in alcohol or flushing it down the toilet, and apply antiseptic to the bite area (www.ncbi.nlm.nih.gov).