Where Alpha-Gal & the Lone Star Tick Are Established
Alpha-gal syndrome, a red-meat allergy triggered by a tick bite, follows the lone star tick, so the map of where the tick is established is the clearest map of where the allergy is spreading. Explore any state below, then read on for how fast it is rising and how common it has become. For the states ranked worst to least, see the alpha-gal risk ranking by state.
The current surge (2025)
The CDC estimates that as many as 450,000 Americans, approaching half a million, may have been affected by alpha-gal syndrome, and calls that a likely undercount. Since 2023, 13 states have made alpha-gal reportable, so the freshest numbers now come from state health departments, and they are climbing fast.
Arkansas: 304 to 3,781
The first state to require reporting (2023) went from 304 cases in 2023 to 3,781 in 2025, a more than 12-fold jump as testing and awareness caught up with the disease.
Martha's Vineyard: 742 positive in 2025
In our own footprint, Martha's Vineyard Hospital ran 1,689 alpha-gal tests in 2025 with 742 positive, up from just two positives in 2020. Rhode Island and Massachusetts now both require reporting.
The tick is pushing north and up the coast, so the Northeast is no longer a safe assumption. Our town and county pages show which ticks, including the lone star, are recorded in each place. Start with the lone star tick guide or check your own town from the location index.
How common is alpha-gal sensitization?
The most rigorous alpha-gal-specific data is a CDC blood-donor study (2024-2025, 300 donors per state) measuring the antibody that marks sensitization. It is not the same as diagnosed allergy, but it shows how sharply risk rises in lone star country. The five highest states averaged 24%.
- Arkansas31.2%
- Missouri26%
- Virginia22.8%
- Kentucky22.7%
- Tennessee21.5%
- Maine10.6%
- South Carolina5.5%
- Minnesota5.4%
- New Mexico1.9%
- Washington1.1%
Source: CDC MMWR — Alpha-Gal IgE Seroprevalence Among Blood Donors, 10 States, 2024–2025. Men were 1.61x more likely to be seropositive than women.
Most saturated states
Share of each state's counties with an established lone star tick population, per CDC ArboNET (2025). This normalizes for state size, so a small heavily-infested state outranks a big one with more raw counties.
- Arkansas97% · 73/75
- Oklahoma90% · 69/77
- Maryland75% · 18/24
- Kentucky72% · 86/120
- Florida72% · 48/67
- Mississippi71% · 58/82
- Illinois67% · 68/102
- New Jersey67% · 14/21
- Delaware67% · 2/3
- Alabama63% · 42/67
- Missouri55% · 63/115
- South Carolina54% · 25/46
- Indiana53% · 49/92
- Virginia52% · 70/134
- North Carolina48% · 48/100
“Established” means a breeding population is documented in that county. Percentages are the share of the state's counties that clear that bar. No record is not proof of absence.
Why the newest national number is from 2022
Alpha-gal syndrome is not a nationally notifiable disease, so CDC has no annual national case count the way it does for Lyme. Its last nationwide study covered 2017 to 2022 (90,018 people with positive tests, concentrated in the southern, midwestern, and mid-Atlantic regions). That is why the live signal has moved to the states: 13 now require reporting, and their 2025 counts, above, are the most current data that exists. Two other honest limits: tick surveillance is county-level and uneven, so “no record” often just means no one trapped there, and we do not invent per-county case numbers that no agency publishes.
Frequently asked questions
- What states have the lone star tick?
- The lone star tick has a documented breeding population in 33 states, plus the District of Columbia (1,139 counties in all), and has been recorded, established or reported, in 39 states per CDC surveillance. It is densest across the Southeast and South-Central US and is spreading north and up the Atlantic coast. It is not established in the West, though isolated specimens have recently turned up in a few western states, including Idaho and California, most likely carried by migratory birds.
- Where is alpha-gal syndrome most common?
- Alpha-gal risk follows the lone star tick, densest across the southern, midwestern, and mid-Atlantic regions. In CDC's 2024-2025 blood-donor study, alpha-gal antibody seroprevalence was highest in Arkansas (31.2%), Missouri, Virginia, Kentucky, and Tennessee. Current state reporting shows the trend: Arkansas alone went from 304 cases in 2023 to 3,781 in 2025.
- Is there an alpha-gal map by county?
- CDC maps lone star tick establishment at the county level, which this page summarizes by state. CDC does not publish a downloadable county-by-county count of alpha-gal cases, so case figures are available only as state and named-county summaries. County-level tick establishment is the most granular programmatic data available.
- Is the lone star tick spreading north?
- Yes. Once a mainly southern tick, it is now established up the mid-Atlantic and into the Northeast, including hotspots on Long Island and coastal New England. Warming winters and deer populations are among the drivers researchers cite.
Lone star tick status by stateLook up any of the 51 states, with alpha-gal seroprevalence where CDC sampled it.
| State | Lone star tick | Counties established | Seroprevalence |
|---|---|---|---|
| Alabama | Established | 42 of 67 | — |
| Alaska | No records | — | — |
| Arizona | No records | — | — |
| Arkansas | Established | 73 of 75 | 31.2% |
| California | No records | — | — |
| Colorado | Reported | 4 reported | — |
| Connecticut | Established | 3 of 8 | — |
| Delaware | Established | 2 of 3 | — |
| District of Columbia | Established | 1 of 1 | — |
| Florida | Established | 48 of 67 | — |
| Georgia | Established | 60 of 159 | — |
| Hawaii | No records | — | — |
| Idaho | No records | — | — |
| Illinois | Established | 68 of 102 | — |
| Indiana | Established | 49 of 92 | — |
| Iowa | Established | 28 of 99 | — |
| Kansas | Established | 32 of 105 | — |
| Kentucky | Established | 86 of 120 | 22.7% |
| Louisiana | Established | 19 of 64 | — |
| Maine | Reported | 12 reported | 10.6% |
| Maryland | Established | 18 of 24 | — |
| Massachusetts | Established | 1 of 14 | — |
| Michigan | Established | 5 of 83 | — |
| Minnesota | Reported | 3 reported | 5.4% |
| Mississippi | Established | 58 of 82 | — |
| Missouri | Established | 63 of 115 | 26% |
| Montana | No records | — | — |
| Nebraska | Established | 27 of 93 | — |
| Nevada | No records | — | — |
| New Hampshire | Established | 1 of 10 | — |
| New Jersey | Established | 14 of 21 | — |
| New Mexico | Reported | 1 reported | 1.9% |
| New York | Established | 19 of 62 | — |
| North Carolina | Established | 48 of 100 | — |
| North Dakota | No records | — | — |
| Ohio | Established | 19 of 88 | — |
| Oklahoma | Established | 69 of 77 | — |
| Oregon | No records | — | — |
| Pennsylvania | Established | 8 of 67 | — |
| Rhode Island | Established | 2 of 5 | — |
| South Carolina | Established | 25 of 46 | 5.5% |
| South Dakota | Established | 4 of 67 | — |
| Tennessee | Established | 45 of 95 | 21.5% |
| Texas | Established | 118 of 254 | — |
| Utah | No records | — | — |
| Vermont | Reported | 4 reported | — |
| Virginia | Established | 70 of 134 | 22.8% |
| Washington | No records | — | 1.1% |
| West Virginia | Established | 13 of 55 | — |
| Wisconsin | Established | 1 of 72 | — |
| Wyoming | Reported | 1 reported | — |
Sources & references
- CDC ArboNET Tick Surveillance — Amblyomma americanum
- CDC MMWR — Alpha-Gal IgE Seroprevalence Among Blood Donors, 10 States, 2024–2025
- Healio — Alpha-gal syndrome expansion and reporting trends (2026)
- Dukes County, MA — AGS reportable; Martha's Vineyard Hospital testing data
- CDC MMWR — Geographic Distribution of Suspected AGS Cases, United States, 2017–2022