Lyme disease is a bacterial disease transmitted by the bite of several United States tick species, including the deer tick, the lone star tick, and the American dog tick. Signs of Lyme disease fall into two categories. Early Lyme disease symptoms follow a pattern of flu-like symptoms accompanied by a rash, while late-stage signs of disseminated Lyme disease include fatigue and neurological symptoms.
The earliest of the signs of Lyme disease is the characteristic Lyme disease rash which appears between three and 30 days following infection. Up to 80% of people with Lyme disease will have this rash, which is called erythema migrans. The rash typically begins as a small patch of redness, which may have a small raised bump at the center. Over the course of several days the rash can expand to a diameter of up to 12 inches (30 cm).
Several other signs of Lyme disease may accompany or follow the appearance of the rash. Often these early symptoms mimic symptoms of the flu, and may include fever and chills, fatigue, headaches, muscle and joint pain, and swollen lymph nodes. Some people may develop one or more erythema migrans in addition to the initial rash.
If these initial symptoms are not diagnosed and the patient is not treated, further symptoms will eventually appear. New symptoms may emerge in days or weeks depending on the individual case. Joint pain and stiffness, heart palpitations, dizziness, and sleep disturbance are possible symptoms at this stage. Some people may experience neurological symptoms such as limb weakness, paralysis, and numbness, seizures, confusion, or Bell’s palsy, characterized by loss of muscle tone in the face. Some symptoms may disappear of their own accord, even if the disease is not treated.
Late signs of Lyme disease may appear after several months. Around 60% of people with untreated Lyme disease will begin to experience episodes of arthritis. This severe pain and swelling usually affects large joints such as the knees. In around 5% of people, neurological symptoms such as memory loss, reduced concentration, and numbness in the hands and feet, may persist for years after the initial infection.
Lyme disease treatment usually entails a course of antibiotics to kill the bacteria causing the disease. If diagnosis is made early enough, a single course of antibiotics is usually enough to cure the patient. A small number of patients may continue to have symptoms such as joint and muscle pain, sleep disturbance, neurological symptoms, and fatigue, following treatment. It is thought these symptoms indicate an autoimmune response triggered by the Lyme disease infection.