How Is Lyme Disease Caused?

Lyme disease is an illness caused by the bacterium Borrelia burgdorferi and is transmitted to humans through the bite of infected black-legged ticks carrying the bacterium. The number of reported cases of Lyme disease, as well as the number of geographic areas in which it is found, has been increasing.

These ticks can also transmit other diseases and infect pets and livestock. Lyme disease is, however, not contagious.1


According to the National Institute of Allergies and Infectious Diseases, Lyme disease is the most common tick-borne infectious disease in the USA.

Causes Of Lyme Disease

To contract Lyme disease, an infected tick must bite you. The adult tick or the young nymph bores a tiny hole in the skin and inserts its mouthparts into the opening, attaching itself to the host. Ticks tend to attach to hard-to-see areas of the human body, such as the scalp, armpits and groin.


When an infected tick bites you, bacteria travels to the tick’s salivary glands and then, enters your skin through the bite, eventually making its way into your bloodstream. The tick’s saliva contains an anesthetic-like substance that numbs your skin so you may not feel the bite.

Generally, the tick must remain attached for at least 24 hours before transmitting the Borrelia burgdorferi bacterium into a human. If you find an attached tick looks swollen, it may have fed long enough to transmit bacteria. Removing the tick as soon as possible may prevent infection.2


Signs And Symptoms Of Lyme Disease

Lyme disease affects different areas of the body in varying degrees as it progresses.

Early Symptoms

  • Fever, chills, headache, fatigue, muscle and joint aches, and swollen lymph nodes.
  • Many people with early-stage Lyme disease develop a distinctive circular rash at the site of the tick bite. This is known as erythema migrans.

Erythema Migrans (EM) Rash:

  • Begins at the site of a tick bite after a delay of 3 to 30 days (average is about 7 days).
  • Expands gradually over a period of days reaching up to 12 inches or more (30 cm) across.
  • May feel warm to the touch, but is rarely itchy or painful.
  • May appear on any area of the body.

Later Signs And Symptoms (days to months after tick bite)

  • Severe headaches and neck stiffness,
  • Additional EM rashes on other areas of the body,
  • Intermittent pain in tendons, muscles, joints, and bones,
  • Heart palpitations or an irregular heart beat (Lyme carditis),
  • Episodes of dizziness or shortness of breath,
  • Facial or Bell’s palsy (loss of muscle tone or droop on one or both sides of the face),
  • Inflammation of the brain and spinal cord,
  • Arthritis with severe joint pain and swelling, particularly the knees and other large joints,
  • Nerve pain,
  • Shooting pains, numbness, or tingling in the hands or feet, and
  • Problems with short-term memory.3

Diagnosis Of Lyme Disease

Lyme disease is diagnosed based on:

  • Signs and symptoms,
  • A history of possible exposure to infected black-legged ticks, and
  • Laboratory blood tests are helpful if used correctly and performed with validated methods.

Prevention Of Lyme Disease

The best way to prevent Lyme disease is to avoid areas where deer ticks live, especially wooded, bushy areas with long grass. There are precautions that you and your family can take to reduce your chances of being bitten by an infected tick:


Cover up – When in wooded or grassy areas, wear shoes, long pants tucked into your socks, a long-sleeved shirt, a hat and gloves.

Use insect repellents – Apply insect repellent with a 20 percent or higher concentration of DEET (diethyltoluamide) to your skin.


Wash Thoroughly – Ticks often remain on your skin for hours before attaching themselves. Showering and using a washcloth might remove unattached ticks, particularly in hard-to-reach areas, that have not yet become engorged.

Early removal of ticks – 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 it and apply antiseptic to the bite area.


Tick-Check – It is advisable to conduct thorough tick checks routinely after outdoor activity.

Check Your Pets – Dogs and cats can get Lyme disease. They can also carry ticks into your home, putting family members at risk. Indoor/outdoor animals should be checked regularly.4

Note – For detailed recommendations on treatment, consult the 2006 Guidelines for treatment developed by the Infectious Diseases Society of America.5