Fig. 1.

Distribution by county of recorded presence of D. variabilis in the contiguous United States based on strict (A) or expanded (B) inclusion criteria. Established counties (in red) have records of six or more ticks or two or more life stages recorded in 1 yr, or using the expanded criteria ≥50 ticks recorded over ≥5 yr if from a state-wide surveillance program. Reported counties (in blue) have records of fewer than six ticks in 1 yr, no documentation of number of ticks, or using the expanded criteria <50 ticks over ≥5 yr if a state-wide surveillance program. Counties shown in white indicate ‘no records’. Notably, an absence of records derived through our review is not indicative of the tick’s absence in a particular county.