I know one of the people who is represented in that table. He got bit in New Jersey, and didn't notice the target growing on his chest until he was driving home, and didn't get treated until he arrived home in Washington (because that's where he's insured; go healthcare). The CDC would count that as a Washington State incident.
See point 3 in the study's stated limitations[1]:
> 3. Surveillance data are captured by county of residence, not county of exposure.
Given that he was 1 of 12 cases in that year, I wouldn't interpret that table as proof that the range of Lyme-infected ticks has spread to Washington state.
