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How Lyme Disease Became Known

Lyme disease was first recognized in 1975 after researchers investigated why unusually large numbers of children were being diagnosed with juvenile rheumatoid arthritis in Lyme, Connecticut, and two neighboring towns. The investigators discovered that most of the affected children lived near wooded areas that harbored ticks. They also found that the children's first symptoms typically started in the summer months coinciding with the height of the tick season. Several of the patients interviewed reported having a skin rash just before developing their arthritis, and many also recalled being bitten by a tick at the rash site.

Further investigations resulted in the discovery that tiny deer ticks infected with a spiral-shaped bacterium or spirochete (which was later named Borrelia burgdorferi) were responsible for the outbreak of arthritis in Lyme.

These spaghetti-like forms shown are B. Burgdorferi isolated from the midgut of a deer tick. This magnified image of the spirochetes was taken with an electron microscope.

Ticks that Most Commonly Transmit B. burgdorferi in the U.S.

(These ticks are all quite similar in appearance.)

Ixodes scapularis: -most common in the northeast and midwest. Also found in the south and southeast.
Ixodes pacificus: -found on west coast.

In Europe, a skin rash similar to that of Lyme disease had been described in medical literature dating back to the turn of the century. Lyme disease may have spread from Europe to the United States in the early 1900s but only recently was recognized as a distinct illness.

The ticks most commonly infected with B. burgdorferi usually feed and mate on deer during the adult part of their life cycle. The recent resurgence of the deer population in the northeast and the influx of suburban developments into rural areas where deer ticks are commonly found have probably contributed to the disease's rising prevalence.

The number of reported cases of Lyme disease, as well as the number of geographic areas in which it is found, has been increasing. Lyme disease has been reported in nearly all states in this country, although most cases are concentrated in the coastal northeast, mid-Atlantic states, Wisconsin and Minnesota, and northern California. Lyme disease is endemic in large areas of Asia and Europe.

Last Updated March 3, 1999 (kap)