What is Lyme disease? Lyme disease is an infectious disease caused by the bacterium Borrelia burgdorferi, which is transmitted through tick bites. The infection resulting from these bites causes swelling, joint pain, rash, and flu-like symptoms. The disease can affect the nervous system, as well, causing headaches, dizziness, and other symptoms. Lyme disease is spread by the deer tick (species Ixodes scapularis) in the northeastern United States and the western black-legged tick (species lxodes pacificus) in the Pacific Northwest. These ticks are typically found in wooded areas where deer are present. The tick carries the Borrelia burgdorferi bacterium, which it passes to humans when it bites them. Lyme disease occurs in approximately 30,000 people each year in the United States (Source: NIAID). Lyme disease begins with the appearance of a red spot at the site of the tick bite within days to weeks following the bite. The spot may expand into a circular or oval-shaped rash and resemble a bull’s-eye: red in the center with alternating circles of white and red around it. This rash is known as erythema migrans and is unique to Lyme disease. Eventually, the rash will spread to different sites on the body. Additional symptoms include fever, aches, stiff neck, and other flu-like symptoms. The symptoms of Lyme disease can be serious and may worsen without treatment. Untreated cases can lead to chronic arthritis (inflammation of the joints), swelling or inflammation of the nerve that controls facial muscles, and even paralysis. Seek prompt medical care if you experience rash, fever, muscle aches, headache, or other symptoms of Lyme disease after being bitten by a tick.