Lyme Disease



Multisystem illness caused by the spirochete Borrelia burgdorferi, carried by the deer tick


  • Can affect people of all ages, but 1/3 to 1/2 of all cases occur in children and adolescents
  • Male/female ratio: 1:1 to 2:1
  • Onset most often in summer months
  • Although Lyme disease can be found anywhere, the majority of the cases in the United States are found in Southern New England and the mid-Atlantic states. It is also seen frequently in California, Minnesota, and Wisconsin.
  • The most common tick-borne disease in the United States, with incidence in 2015 of 8.9/100,000.
    • However, incidence varies significantly in different parts of the country and 95% of all cases reported were found in 14 states: Connecticut, Delaware, Maine, Maryland, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Virginia.
    • Outside of those states, Lyme disease remains rare.

Risk Factors


Chronic Lyme arthritis seems to be associated with increased incidence of HLA-DR4 and less so with HLA-DR2.


  • B. burgdorferi is injected into skin with saliva during bite of Ixodes tick.
  • Spirochetes first migrate within skin, forming the typical rash, erythema migrans.
  • Spirochetes then spread hematogenously to other organs, including heart, joints, and nervous system.


The tick-borne spirochete B. burgdorferi

Commonly Associated Conditions

The same ticks that transmit Lyme disease can also transmit Ehrlichia and Babesia, so infections with those spirochetes can occur simultaneously.

There's more to see -- the rest of this topic is available only to subscribers.