Lyme disease is an illness that’s caused by bacteria carried by infected ticks. If you’ve been bitten by a tick and show any of the early symptoms of Lyme disease, you should see your doctor. Lyme disease has three stages: Early localized Early disseminated Late Early-localized stage Lyme disease Typically, a large, raised, red spot (erythema migrans) appears at the site of the bite, usually on the thigh, buttock, or trunk or in the armpit. The spot usually disappears after about 3 to 4 weeks. About 25% of infected people never develop—or at least never notice—the characteristic red spot. Early-disseminated stage Lyme disease This stage begins when the bacteria spread through the body. Fatigue, chills, fever, headaches, stiff neck, muscle aches, and painful, swollen joints are common. In nearly half of people who are not treated, more, usually smaller erythema migrans spots appear on other parts of the body.People have a backache, nausea, vomiting, sore throat, swollen lymph nodes, and an enlarged spleen. The nervous system is affected in about 15% of people. Common problems are meningitis and Bell palsy. About 8% of infected people have irregular heartbeats (arrhythmias) and inflammation of heart tissue (myocarditis) and the sac around the heart (pericarditis) with chest pain. Irregular heartbeats may cause palpitations, light-headedness, or fainting. Late stage Lyme disease If the initial infection is untreated, other problems develop months to years later. Arthritis develops in more than half of people, usually within several months. Swelling and pain typically recur in a few large joints, especially the knee, for several years. Cysts may develop and rupture behind the knees, suddenly increasing the pain. A few people develop abnormalities related to brain and nerve malfunction. Mood, speech, memory, and sleep may be affected.