Lyme disease is infectious and spread from bacteria carried by some ticks.
Borrelia is a genus of bacteria of the spirochete phylum . It causes borreliosis , a zoonotic , vector-borne disease transmitted primarily by ticks and by lice , depending on the species . Lyme disease . The most common sign of infection is an expanding area of redness on the skin , known as erythema migrans , that begins at the site of a tick bite about a week after it has occurred .