ABSTRACT
Lyme disease is caused by a Gram-negative, spirochetal bacterium from the genus Borrelia (Figure 13.1). There are more than 37 species in the genus, several of which cause Lyme disease in humans, including B. burgdorferi in the United States and parts of Europe and B. afzelii and B. garinii in Europe and Asia (Oliver et al. 2003). Borrelia species has been classied into two groups based on genetic differences: a Lyme disease group, which are discussed in this chapter, and the relapsing fever group, which are discussed in Chapter 14.
