Definition: Lyme Disease is an infectious disease caused by at least three species of bacteria belonging to the genus Borrelia.  Borrelia burgdorferi sensu lato is the main cause of Lyme disease in the United States. 
Other Names: lyme borreliosis 
Lyme disease is the most common tick-borne disease in the Northern Hemisphere. Borrelia is transmitted to humans by the bite of infected ticks. Nymphal and adult deer ticks can be carriers of Lyme disease. The ticks pick up the bacteria when they bite mice or deer that are infected with Lyme disease.  Cases of Lyme disease have now been reported in most parts of the United States. Most of the cases occur in the Northeast, upper Midwest, and along the Pacific coast. This is where ticks are most prevalent. Lyme disease is usually seen during the late spring, summer, and early fall. 
You’re more likely to get Lyme disease if you live or spend time in the grassy and heavily wooded areas where ticks carrying the disease breed. 
Everyone who has been bitten by a tick should be watched closely for at least 30 days. Most people who are bitten by a tick do NOT get Lyme disease. 
Lyme disease is the most common tick-borne disease in North America and Europe and one of the fastest-growing infectious diseases in the United States. Of cases reported to the United States CDC, the ratio of Lyme disease infection is 7.9 cases for every 100,000 persons. In the ten states where Lyme disease is most common, the average was 31.6 cases for every 100,000 persons for the year 2005. 
Signs and Symptoms
Lyme disease signs and symptoms vary widely because Lyme disease can affect various parts of the body. Not everyone with the disease will have all of the signs and symptoms, and some individuals may be asymptomatic. There are 3 stages of Lyme Disease.  Common and characteristic symptoms of Lyme disease include:
Rash. A small, red bump may appear within a few days to a month, often at the site of the tick bite. Tick bites most often occur in your groin, belt area or behind your knee. It may be warm to the touch and mildly tender. Over the next few days, the redness expands, forming a rash that may be as small as your fingertip or as large as 12 inches (30 centimeters) across. It often resembles a bull’s-eye, with a red ring surrounding a clear area and a red center. The rash, called erythema migrans,  is one of the hallmarks of Lyme disease, affecting about 70 percent to 80 percent of infected people. If you’re allergic to tick saliva, redness may develop at the site of a tick bite that usually fades within a week. This is not the same as erythema migrans, which tends to expand and get redder over time.
Flu-like symptoms. A fever, chills, fatigue, body aches and a headache may accompany the rash. These are often the first symptoms noted, and occur during the first stage of Lyme disease infection. 
Migratory joint pain. If the infection is not treated, you may develop bouts of severe joint pain and swelling several weeks to months after you’re infected. Your knees are especially likely to be affected, but the pain can shift from one joint to another. 
Neurological problems. Acute neurological problems, which appear in 15% of untreated patients, encompass a spectrum of disorders. Iinflammation of the membranes surrounding your brain (meningitis), temporary paralysis of one side of your face (Bell’s palsy), numbness or weakness in your limbs, and impaired muscle movement may occur weeks, months or even years after an untreated infection. Memory loss, difficulty concentrating, and changes in mood or sleep habits also can be symptoms of late-stage Lyme disease. 
When to See your Doctor
If you know you’ve been bitten and experience signs and symptoms of Lyme disease — particularly if you live in an area where Lyme disease is prevalent — contact your doctor immediately. Treatment for Lyme disease is most effective if begun early. 
Tests and Diagnosis
Lyme disease is frequently overdiagnosed. Its variable signs and symptoms are nonspecific and are often found in other conditions.  If you don’t have the characteristic Lyme disease rash lab tests to identify antibodies to the bacteria may be used to help confirm the diagnosis. These tests are most reliable a few weeks after an infection, after your body has time to develop antibodies. Even then, however, the tests aren’t entirely foolproof. 
Enzyme-linked immunosorbent assay (ELISA) test. The test used most often to detect Lyme disease, ELISA detects antibodies to B. burgdorferi. But because it can sometimes provide false-positive results, it’s not used as the sole basis for diagnosis. 
Western blot test. If the ELISA test is positive, another test (usually the Western blot) is done to confirm the diagnosis. The Western blot detects antibodies to several proteins of B. burgdorferi. 
Polymerase chain reaction (PCR). This test helps detect bacterial DNA in fluid drawn from an infected joint. It’s not effective at detecting infection of blood or urine. It’s used for people who may have chronic Lyme arthritis. It may also be used to detect persistent infection in the cerebrospinal fluid of people who have nervous system symptoms  (muscle weakness, memory loss).
Treatment for Lyme diseases involves oral or, in serious cases, intravenous antibiotics. A single dose of antibiotics may be offered to someone soon after being bitten by a tick, especially if all of the following are true:
A full course of antibiotics is used to treat people who are proven to have Lyme disease. The specific antibiotic used depends on the stage of the disease and the symptoms. 
The Food and Drug Administration (FDA) warns consumers and health care providers to avoid bismacine, an injectable compound prescribed by some alternative medicine practitioners to treat Lyme disease. Bismacine, also known as chromacine, contains high levels of the metal bismuth. Although bismuth is safely used in some oral medications for stomach ulcers, it’s not approved for use in injectable form or as a treatment for Lyme disease. Bismacine can cause bismuth poisoning, which may lead to heart and kidney failure.