Lyme Disease and Related Tick-Borne Infections - Risk Factors

One interesting report found that the blood of the Western fence lizard contains a chemical that destroys B. burgdorferi, the Lyme disease spirochete. The presence of this lizard may help explain the low incidence of Lyme disease in western states. Experts differ on whether Lyme disease exists with any significance in the southern United States. A Lyme-like disease has been reported in the south (Mississippi, South Carolina, Georgia, Florida, and Texas), which apparently responds to antibiotics (as Lyme does). Researchers have also identified spirochetes on Lone Star ticks that appear to belong to the Borrelia family. Studies are underway to determine the exact nature and extent of this condition.

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Worldwide Locations. Pockets of Lyme disease exist around the world. The disease is common in Europe, particularly in forested areas of middle Europe and Scandinavia. The Borrelia family is also responsible for tick infections in Europe, but different subspecies (B. garinii and B. afzelii) may be more common there and cause slightly different symptoms. The infection has also been reported in Russia, China, and Japan.

High-Risk Landscapes

One analysis suggested the risk for Lyme disease exposure is highest in wet, green areas, and lower in areas with lawns or low vegetation. Hiking and camping in the Northeastern woods carries a significant risk for tick bites and Lyme disease.

The disease is not limited to rural settings. It is becoming increasingly common in suburban areas. Beaches are also home to ticks.

Time of Year

The time of year of highest risk depends on the geographical region.

Northeast and North Central U.S. In the northeastern and north central U.S., most cases of Lyme disease are reported from May through August, with July being the peak month.

Exceptions may occur in years of warm winters and wet springs, which can bring the deer tick nymphs out about 2 weeks earlier. This same climate also creates the wet, green environment that increases the prevalence of ticks.

Noncoastal Western States. In the noncoastal western U.S., the disease most often occurs between January and May.

West Coast. The risk is higher on the west coast between November and April.