United States · 2025 CDC data

Alpha-gal syndrome risk, state by state

Alpha-gal syndrome, the red-meat allergy set off by a tick bite, follows one tick: the lone star tick. There is no honest state ranking of alpha-gal cases (the CDC does not publish one), but the tick that causes it is tracked county by county nationwide. So the map of where that tick is established is the clearest map of where the allergy is spreading, and it gives every state a place in line. As many as 450,000 Americans may already be affected.

Widely establishedExpandingFrontierNo records

The ranking

Every state, ranked by tick establishment

Ordered by the share of each state's counties where the lone star tick has an established breeding population, per CDC ArboNET (2025). This normalizes for state size, so a small, heavily-infested state outranks a big one with more raw counties. Seroprevalence, where shown, is the share of blood donors carrying the alpha-gal antibody in CDC's 2024–2025 study.

U.S. states ranked by share of counties with an established lone star tick population, with alpha-gal seroprevalence where CDC sampled it
#	State	Established	Seroprevalence	Tier
1	Arkansasreportable73 of 75 counties established	97%	31.2%	Widely established
2	Oklahoma69 of 77 counties established	90%	—	Widely established
3	Maryland18 of 24 counties established	75%	—	Widely established
4	Kentucky86 of 120 counties established	72%	22.7%	Widely established
5	Florida48 of 67 counties established	72%	—	Widely established
6	Mississippi58 of 82 counties established	71%	—	Widely established
7	Illinois68 of 102 counties established	67%	—	Widely established
8	New Jersey14 of 21 counties established	67%	—	Widely established
9	Delaware2 of 3 counties established	67%	—	Widely established
10	Alabama42 of 67 counties established	63%	—	Widely established
11	Missouri63 of 115 counties established	55%	26%	Widely established
12	South Carolina25 of 46 counties established	54%	5.5%	Widely established
13	Indiana49 of 92 counties established	53%	—	Widely established
14	Virginia70 of 134 counties established	52%	22.8%	Widely established
15	North Carolina48 of 100 counties established	48%	—	Expanding
16	Tennessee45 of 95 counties established	47%	21.5%	Expanding
17	Texas118 of 254 counties established	46%	—	Expanding
18	Rhode Islandreportable2 of 5 counties established	40%	—	Expanding
19	Georgia60 of 159 counties established	38%	—	Expanding
20	Connecticut3 of 8 counties established	38%	—	Expanding
21	New York19 of 62 counties established	31%	—	Expanding
22	Kansas32 of 105 counties established	30%	—	Expanding
23	Louisiana19 of 64 counties established	30%	—	Expanding
24	Nebraska27 of 93 counties established	29%	—	Expanding
25	Iowa28 of 99 counties established	28%	—	Expanding
26	West Virginia13 of 55 counties established	24%	—	Expanding
27	Ohio19 of 88 counties established	22%	—	Expanding
28	Pennsylvania8 of 67 counties established	12%	—	Frontier
29	New Hampshire1 of 10 counties established	10%	—	Frontier
30	Massachusettsreportable1 of 14 counties established	7%	—	Frontier
31	Michigan5 of 83 counties established	6%	—	Frontier
32	South Dakota4 of 67 counties established	6%	—	Frontier
33	Wisconsin1 of 72 counties established	1%	—	Frontier
34	Colorado0 of 64 counties established	0%	—	Frontier
35	Maine0 of 16 counties established	0%	10.6%	Frontier
36	Minnesota0 of 87 counties established	0%	5.4%	Frontier
37	New Mexico0 of 33 counties established	0%	1.9%	Frontier
38	Vermont0 of 14 counties established	0%	—	Frontier
39	Wyoming0 of 23 counties established	0%	—	Frontier

“Established” means CDC documents a breeding population in that county. States not listed have no lone star record in CDC surveillance, which is an absence of records, not proof the tick is absent. No record often just means no one has trapped there.

Reading the tiers

Three different stories in one ranking

Where a state lands changes what its alpha-gal story is. Each tier is a different headline.

Widely established

14 states

The lone star tick is established in at least half the state's counties. This is core alpha-gal country.

Expanding

13 states

Established across a growing share of counties, on the way up but not yet saturated.

Frontier

12 states

A thin but real foothold, often just a handful of counties. In the North, a single new county is a local headline.

The clearest single trajectory is 2023→2025 in Arkansas, the first state to require reporting: 304 cases became 3,781, a more than 12-fold jump as testing and awareness caught up with the disease.

The northward push

Where the tick has moved north

The most locally newsy part of the map is the northern edge, where the lone star tick was considered out of range a generation ago. These are the counties in the Northeast and Mid-Atlantic where CDC now classifies it as established, from New Jersey, where it is already in most counties, down to Massachusetts, where it holds a single one. Each is a “the tick is here” anchor for a local story.

New Jersey

14 of 21 counties · 67% established

Atlantic County, Burlington County, Camden County, Cape May County, Cumberland County, Gloucester County, and 8 more.

Rhode Island

#18

2 of 5 counties · 40% established

Bristol County, Newport County.

Connecticut

#20

3 of 8 counties · 38% established

Fairfield County, New Haven County, New London County.

New York

#21

19 of 62 counties · 31% established

Albany County, Broome County, Cattaraugus County, Chautauqua County, Columbia County, Delaware County, and 13 more.

Pennsylvania

#28

8 of 67 counties · 12% established

Bucks County, Chester County, Dauphin County, Delaware County, Erie County, Franklin County, and 2 more.

New Hampshire

#29

1 of 10 counties · 10% established

Merrimack County.

Massachusetts

#30

1 of 14 counties · 7% established

Dukes County.

Massachusetts is the sharpest example: the tick is established in a single county, Dukes (Martha's Vineyard), where the local hospital ran 1,689 alpha-gal tests in 2025 with 742 positive, up from just two positives in 2020.

The case data

Where the suspected cases cluster

The establishment map ranks the vector. Underneath it, CDC's one national study of suspected alpha-gal cases (2017–2022) names the two counties carrying the heaviest recorded burden, and the leader is a surprise: a Long Island suburb, not a Southern county.

Suffolk County, New York

3,746

suspected cases, about 4% of the entire U.S. total, the highest of any county in the country.

Bedford County, Virginia

1,511

suspected cases, the second-highest county nationwide.

Nationwide, 90,018 of 295,400 people tested (30.5%) returned a positive alpha-gal antibody test over those six years, concentrated in the southern, midwestern, and mid-Atlantic regions.

“Suspected” here means a positive alpha-gal IgE lab test, not a confirmed diagnosis, and the count reflects where testing happens as much as where the allergy is. It is CDC's own metric, and the only county-level case data that exists.

The honest limits

Why this ranks the tick, not the cases

Two guardrails travel with every number here.

Alpha-gal syndrome is not a nationally notifiable disease, so the CDC has no annual national case count the way it does for Lyme. Its last nationwide study covered 2017–2022 (90,018 people with positive tests, concentrated in the southern, midwestern, and mid-Atlantic regions). Since 2023, the live signal has moved to the states: 13 now require reporting. So this page ranks the vector, the lone star tick, because that is the strongest state-comparable, all-states measure that exists.

Establishment is a tick-surveillance status, not a diagnosis, and “not established” is never proof a county is safe. Surveillance is county-level and uneven. We do not invent per-county case numbers that no agency publishes.

Explore the map

For the interactive, click-any-state version of this data, with the current surge and full seroprevalence chart, see the lone star & alpha-gal map. To understand the allergy itself, start with the alpha-gal syndrome guide.

Using this in a story?

Free to cite with attribution and a link to TickZone. Every figure traces to CDC surveillance and the sources below.

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