Lyme disease is hardly a household word. In fact, unless you live in the Northeastern United States, you might not have heard of this potentially serious and somewhat mysterious illness. Lyme disease is an infection transmitted solely by tick bites. But don't cringe in fear the next time a friend suggests a walk in the woods. Only two species of ticks, both belonging to the "Ixode" genus, are carriers: deer ticks (Ixodes scapularis), and black-legged ticks (Ixode pacificus). Ixode ticks are found mainly on deer, although field mice, rabbits, sheep, and cattle may also pick them up.

The tick itself is not to blame for the infection, but a small, spiral-shaped bacteria called Borrelia burgdorferi that lives inside the tick. Named for the town of Lyme, Connecticut, where it was first identified back in the early 1970's, Lyme disease has appeared in the Northeast, the Mid-Atlantic, the Pacific Northwest, Wisconsin, and Minnesota.(1) Lyme disease was discovered when young children living in the Lyme area began showing up in doctors' offices suffering from unexplained bouts of arthritis. After researching these puzzling cases, medical experts traced the problem to tick bites in the children and subsequently identified the guilty bacteria.(2)

Lyme disease is a challenging illness, both to diagnose and to treat. It is a difficult disease for clinicians to spot. For one thing, Ixode ticks are extremely small, about the size of a pinhead, making them hard to see, especially on areas of the body with hair. What's more, tick bites are virtually painless, so people often have no idea they've been bitten.

The infection usually produces no symptoms at first. In about half the cases, a rash appears at the site of the bite. Called a "bull's eye," this rash is the only visible sign of Lyme disease. Blood tests may not be reliable, since it takes up to four weeks after exposure before antibodies can be found in the blood. After several weeks, a highly sensitive test called "ELISA" can be used to diagnose Lyme disease more accurately. This is followed up with a "Western blot" test for confirmation. A new genetic engineering technique called "PCR" is being developed that can detect genetic material from the Lyme bacteria in tissue, blood, and body fluids.(3)

The symptoms of Lyme disease mimic many other illnesses, adding to the challenge physicians face in diagnosing it correctly. Lyme disease is often misdiagnosed as chronic fatigue syndrome, fibromyalgia, depression, or multiple sclerosis.