Lyme disease is the most common vector-borne disease in the United States. The infection is caused by Borrelia burgdorferi, a bacteria-like organism called a spirochete which is endemic in at least 15 states. Transmission to humans occurs by the bite of an infected deer tick. The tick responsible for transmitting Lyme disease in humans in the Northeast and North Central regions is Ixodes scapularis and in the west is the Ixodes pacificus. Deer ticks are much smaller than dog ticks. The nymph and larvae stages of Ixodes scapularis are about 1 mm in size. This is about the size of a pin head. Ticks feed by inserting their mouth parts into the host and taking a blood meal. The longer a tick is attached, the more likely it is to transmit Lyme disease.
The risk of Lyme disease in the United States is well localized to three areas: the Northeast from Maine to Maryland, the Midwest, specifically, Wisconsin and Minnesota and the Northwest, specifically Northern California and parts of Oregon. Lyme disease is the leading vector-borne illness in the United States, with approximately 15,000 cases reported every year. Although cases have been reported in 49 states and the District of Columbia, 90% of cases occurred in ten states.
Fire fighters who work and live in these areas are at increased risk of getting Lyme disease. Fire fighters who are surrounded by woods or overgrown brush, or who participate in outdoor recreational activities such as hunting, camping, fishing, or hiking are at increased risk of Lyme disease. Preventive measures can reduce the chance of being bitten by a tick.