The incubation period for Lyme disease ranges from
3 to 32 days after a bite from an infected tick. In roughly 80 percent of cases, the disease first presents itself with a red skin rash-called erythema migrans-at the site of the bite. The rash expands out from the bite in a circular pattern over the course of several days and often becomes bright red on its outer edge, forming a bull's-eye pattern. At this stage, patients may also experience a number of flulike symptoms, including:
> Muscle or joint aches and pains
When treated at this stage, Lyme disease quickly yields to antibiotics.
If not promptly treated with antibiotics, the Lyme bacteria may spread to the skin, joints, nerves, and heart. Symptoms at this point can include:
> Stiff neck
> Paralysis of facial muscles (Bell's palsy)
> Heart palpitations
> Joint and muscle pains
> Arthritis, often in the knees
> Debilitating fatigue or malaise
> Nerve pain
> Heart block (a condition that impairs the trans-mission of electrical signals in the heart)
Most stage 2 cases respond well to antibiotics, though in the worst cases, symptoms may linger after treatment.
If Lyme disease remains untreated or undertreated, symptoms may persist for a year or more after the initial tick bite. Late-stage Lyme can spur symptoms such as:
> Intermittent, chronic arthritis, most commonly in the knees
> Memory impairment
> Numbness or tingling in the hands or feet
> Mood and sleep disturbances
> Sensory loss
> Diminished reflexes
Some evidence suggests that symptoms at this stage may stem from the body's immune response to the Lyme bacteria, though this theory is not yet proven. Even without treatment, most stage 3 cases eventually improve on their own.