Figure 1. County-level distribution of Ixodes scapularis ticks and Borrelia burgdorferi–infected I. scapularis ticks in upper Tennessee Valley, USA, 2006 and 2017. A county was classified as having an established I. scapularis population if >6 I. scapularis adult ticks or ticks of 2 life stages were collected in that county. A county was classified as having I. scapularis ticks reported if 1–5 I. scapularis ticks of a single life stage were collected in that county. A county was classified as infected if I. scapularis ticks infected with B. burgdorferi were detected in that county. A) I. scapularis ticks in 2006 (2), determined by collecting ticks from hunter-harvested deer. B) I. scapularis ticks in 2017 determined by drag-cloth surveying during the peak of adult tick activity (late October–January).