| lyme disease: a growing threat to urban populations. | lyme disease or lyme borreliosis, which is caused by three groups of the spirochete borrelia burgdorferi, is transmitted in north america, europe, and asia by ticks of the ixodes ricinus complex. the primary areas around the world that are now affected by lyme disease are near the terminal moraine of the glaciers 15,000 years ago. the emergence of lyme disease in the united states in this century is thought to have occurred because of ecological conditions favorable for deer. from 1982 through 1 ... | 1994 | 8146126 |