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What Is Lyme Disease?

First identified in a group of children in Lyme, Conn., Lyme disease has now been found in nearly all states and 18 other countries. Greater than 90% of cases are reported in three areas:

• Northeast, from Massachusetts to Maryland.
• North Central States, mostly in Minnesota and Wisconsin.
• West Coast. particularly Northern California.

Because the symptoms are random and vague (aside from a bull's-eye rash), Lyme disease can be hard to diagnose. Unfortunately, unless Lyme disease is treated promptly, it can also be difficult to cure. For these reasons, people living in high-risk areas have considerable anxiety about Lyme disease, and doctors tend to over diagnose it.

What Causes It?

Lyme disease is caused by a bacterium that is transmitted through the bite of the tiny deer tick in the East and Central U.S. and the western black-legged tick in the Pacific West. The riskiest months for Lyme disease are from May through September, since that's when the young ticks are likely to be biting.

In the body, the bacteria may cause flu-like symptoms, invade many tissues — including the heart and nervous system — and trigger an immune response that leads to Lyme arthritis.

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