Tick Range Expansion: What the Maps Show

The CDC keeps county-by-county maps for each main tick species, updated through 2024. The pattern's the same no matter which tick you look at.

Deer Tick (Black-Legged Tick)

These have pushed well into the Midwest by now and they're still moving. And it's not just spreading to new places, the ticks in areas they've already been for years are getting thicker on the ground too. The Northeast in particular has seen way more ticks per acre even in spots that have had them forever.

Lone Star Tick

This is the big one. The lone star tick used to be a Southeast thing. Now it's set up shop all through the Mid-Atlantic and it's working its way into southern New England and the Midwest. Funny enough, it actually covered most of the eastern US back in the 1750s. Deer populations crashed for a long stretch and took the tick down with them, but as deer numbers climbed back over the last 80 years or so, the lone star tick came right back along with them. Wherever the deer go, this tick follows.

A piece in the New England Journal of Medicine tracked the lone star tick showing up in the Northeast and pointed out that in spots where it overlaps with the deer tick, it can actually become the more common one. It's a meaner feeder than the deer tick, bites people at every stage of its life including as a tiny larva, and it'll set up in all kinds of places, suburban yards included, not just deep woods. This spread is the same thing driving the rise in alpha-gal cases I talk about on the alpha-gal page.

A New Bug to Watch For

The Companion Animal Parasite Council's 2026 report flagged a new tick-borne bacteria, called Rickettsia finnyi, showing up in dogs across the Southeast and Midwest with symptoms that look a lot like Rocky Mountain spotted fever. First spotted in dogs back in 2018, and they think the lone star tick is carrying it around. As that tick keeps spreading, whatever it's carrying spreads with it.