You've been out in the woods or along the edge of the woods.  Or playing with your dog.  Or maybe someone else in your house has been out in the woods, or playing with your dog. 

A few days later, you find a bull's eye-shaped rash on your arm.

This is when smart kids go to the doctor and get tested for Lyme disease.  You can catch it when a blacklegged tick latches onto you to do what ticks do best:  biting into your skin and sucking blood.

When it does, sometimes it transmits a tiny bacterium called Borrelia burgdorferi into your body.  This is the bacterium that causes Lyme disease.

Lyme disease occurs mainly in suburban areas--or even in city parks--where there are lots of wild deer.  Adult ticks obtain their blood meals from large or medium-sized mammals, and large deer populations make it easy for the ticks to find a quick bite!

But adult ticks usually aren't responsible for spreading Lyme disease to people.  Generally, tick larvae pick up the bacterium from feeding on infected mice or other small animals.

Then the larvae become nymphs that lurk in the grass, on fallen logs, or in other good hiding places.  When any suitable animal--such as a bird, a lizard, a deer, a dog, or a person--passes by, a nymph latches on to score a snack.