Lyme disease affects 300,000 Americans each year, the U.S. Centers for Disease Control and Prevention reports.
Ninety-six percent of all Lyme disease cases cluster in 13 states: Connecticut, Delaware, Maine, Maryland, Massachusetts, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Vermont, Virginia and Wisconsin. Elsewhere, the risk is very low.
Only 80 percent of Lyme disease cases come with the target-shaped skin rash. Like most bacterial infections, Lyme disease can cause fever, chills, headache, muscle and joint pain and swollen lymph nodes.
Not all ticks carry the Lyme-spreading bacterium, and not all ticks that carry the bug transmit it. The CDC says that in most cases, the tick must be attached for 36-48 hours or more for the bacterium to be transmitted.
The CDC says blood tests for Lyme disease have "very good sensitivity," though they do have their limits. The tests look for antibodies in the blood, so they can return false negatives during the first few weeks after exposure.
The typical treatment is a brief bout of oral antibiotics, though some patients with other conditions might need IV treatments, the CDC says. One in five patients have "post-treatment Lyme disease syndrome," and can feel ill for months.
Although up to 20 percent of Lyme disease patients will have post-treatment Lyme disease syndrome, most experts believe that it's the result of damage to tissues during the infection rather than a persistent infection.