Tick risk is not uniform across the United States. The species you are most likely to encounter, the diseases they carry, and the time of year they are most active all depend heavily on where you live, work, and recreate. A hiker in coastal Maine faces a very different threat profile than a rancher in Arizona or a trail runner in the Pacific Northwest.
This guide provides a regional breakdown of the dominant tick species, primary disease risks, and peak activity windows for five major regions of the United States. Use it to understand what you are up against before you head outdoors.
The Northeast
States: Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania, Delaware, Maryland
Dominant Tick Species: Blacklegged (Deer) Tick (Ixodes scapularis), Lone Star Tick (Amblyomma americanum), American Dog Tick (Dermacentor variabilis)
The Northeast is the epicenter of tick-borne disease in the United States. The blacklegged tick is firmly established across the region, and its range continues to expand northward and inland. In 2023, the CDC reported over 89,000 cases of Lyme disease nationally, with the highest concentrations in the Northeast. States like Pennsylvania (16,671 cases), New York (22,173 cases), and New Jersey consistently rank among the top five nationally for Lyme disease burden.
Primary Disease Risks:
- Lyme Disease (Borrelia burgdorferi): The dominant concern throughout the region. Transmitted by blacklegged tick nymphs and adult females.
- Anaplasmosis (Anaplasma phagocytophilum): Increasingly common, particularly in New England and the Hudson Valley. Rapid onset, often misdiagnosed as flu.
- Babesiosis (Babesia microti): A malaria-like parasitic infection transmitted by the blacklegged tick. Especially dangerous for the elderly and immunocompromised.
- Powassan Virus: Rare but serious. Cases have been rising in the Northeast, particularly in New York and New England. Transmission can occur in as little as 15 minutes of tick attachment.
- Ehrlichiosis: Transmitted by the Lone Star tick, which has expanded significantly into the mid-Atlantic and southern New England states.
- Rocky Mountain Spotted Fever (RMSF): Transmitted by the American dog tick. Less common in the Northeast than other regions but present.
Peak Activity Windows:
Key Awareness: Nymphal blacklegged ticks are the size of a poppy seed and responsible for the majority of Lyme disease transmissions in this region. A thorough full-body tick check after any outdoor activity is essential from May through July.
The Upper Midwest
States: Minnesota, Wisconsin, Michigan, Iowa, Illinois, Indiana, Ohio
Dominant Tick Species: Blacklegged (Deer) Tick (Ixodes scapularis), Lone Star Tick (Amblyomma americanum), American Dog Tick (Dermacentor variabilis)
The Upper Midwest has emerged as one of the highest-risk regions in the country for tick-borne disease. Minnesota recorded 3,551 confirmed Lyme disease cases in 2024, a 21 percent increase from 2023, and Wisconsin consistently ranks among the top five states nationally. The blacklegged tick is now well-established across north-central and east-central Minnesota, the northern Great Lakes region of Wisconsin and Michigan, and is expanding southward into Illinois and Indiana.
Primary Disease Risks:
- Lyme Disease: The primary concern across the northern tier of the region.
- Anaplasmosis: Extremely common in the Upper Midwest. Minnesota reported 627 confirmed cases in 2024.
- Babesiosis: Present and increasing. Minnesota reported 89 confirmed cases in 2024.
- Powassan Virus: Minnesota recorded 14 confirmed cases in 2024, a new state record.
- Ehrlichiosis: Transmitted by the Lone Star tick, which has expanded into the southern portions of the region.
Peak Activity Windows:
Key Awareness: Tick season in Minnesota and Wisconsin now runs from early spring through late fall, and ticks can remain active on warm winter days when temperatures exceed 35 degrees Fahrenheit. Do not assume the season is over after the first frost.
The Southeast and Deep South
States: Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana, Arkansas, Tennessee, Kentucky, Texas, Oklahoma
Dominant Tick Species: Lone Star Tick (Amblyomma americanum), American Dog Tick (Dermacentor variabilis), Brown Dog Tick (Rhipicephalus sanguineus), Gulf Coast Tick (Amblyomma maculatum), Blacklegged Tick (Ixodes scapularis, southern variant)
The Southeast is the heartland of the Lone Star tick, one of the most aggressive human-biting ticks in North America. The region also carries a disproportionate burden of Rocky Mountain Spotted Fever, which is most deadly in the southeastern United States.
Primary Disease Risks:
- Ehrlichiosis: The dominant tick-borne disease concern in the Southeast, transmitted by the Lone Star tick.
- Rocky Mountain Spotted Fever (RMSF): Case fatality rate of 20 to 25 percent if untreated, making it the most lethal tick-borne disease in the U.S.
- Alpha-Gal Syndrome: The Lone Star tick is the primary vector for this red meat allergy. Cases are concentrated in the Southeast and mid-Atlantic states.
- Heartland Virus and Bourbon Virus: Rare but serious emerging tick-borne viruses transmitted by the Lone Star tick.
- Tularemia: The South-Central states have historically reported the highest tularemia rates.
- STARI (Southern Tick-Associated Rash Illness): A bull’s-eye rash that can follow a Lone Star tick bite, distinct from Lyme disease.
Peak Activity Windows:
Key Awareness: The Lone Star tick does not transmit Lyme disease, but it does cause a bull’s-eye rash (STARI) that can be mistaken for it. Inform your physician of the tick species if known, as treatment protocols may differ.
The Pacific Coast and Pacific Northwest
States: California, Oregon, Washington
Dominant Tick Species: Western Blacklegged Tick (Ixodes pacificus), Pacific Coast Tick (Dermacentor occidentalis), Rocky Mountain Wood Tick (Dermacentor andersoni, eastern Washington and Oregon)
Primary Disease Risks:
- Lyme Disease: Present but less prevalent than in the Northeast. California reports several hundred confirmed cases annually.
- Anaplasmosis: Transmitted by the western blacklegged tick.
- Rocky Mountain Spotted Fever: Transmitted by the Pacific Coast tick.
- Colorado Tick Fever: A viral disease transmitted by the Rocky Mountain wood tick in eastern Oregon and Washington.
- Tick Paralysis: Both the Pacific Coast tick and Rocky Mountain wood tick can cause this neurotoxic condition.
Peak Activity Windows:
Key Awareness: The western blacklegged tick has an unusual seasonal pattern: adult ticks are most active in fall and winter, not summer. Hikers and outdoor workers in California and Oregon should be aware that tick risk does not disappear when the weather cools.
The Mountain West and High Plains
States: Montana, Idaho, Wyoming, Colorado, Utah, Nevada, New Mexico, Arizona, South Dakota, North Dakota, Nebraska, Kansas
Dominant Tick Species: Rocky Mountain Wood Tick (Dermacentor andersoni), American Dog Tick (Dermacentor variabilis), Brown Dog Tick (Rhipicephalus sanguineus), Soft Ticks (Ornithodoros spp.)
Primary Disease Risks:
- Rocky Mountain Spotted Fever: The Mountain West is the native range of the Rocky Mountain wood tick, the original RMSF vector.
- Colorado Tick Fever: A viral disease unique to the Mountain West, found at elevations of 4,000 to 10,500 feet. Not treatable with antibiotics.
- Tularemia: The Mountain West and south-central states report the highest tularemia rates in the country.
- Tick Paralysis: The Rocky Mountain wood tick is the primary cause of tick paralysis in the United States. Can be fatal if the tick is not found and removed. Symptoms resolve within hours of removal.
- Tick-Borne Relapsing Fever (TBRF): Transmitted by soft ticks in rustic cabins, caves, and rodent-infested structures throughout the Mountain West.
Peak Activity Windows:
Key Awareness: Soft ticks feed quickly at night, often while a person is sleeping, and detach before morning. If you wake up in a rustic cabin or backcountry shelter with unexplained bite marks and develop a high fever within a week, tick-borne relapsing fever should be considered and a physician consulted promptly.
Summary: Regional Risk at a Glance
Regardless of region, the fundamentals of tick bite prevention remain the same: wear permethrin-treated clothing, apply an EPA-registered repellent to exposed skin, perform a full-body tick check after every outdoor outing, and remove any attached tick promptly. What changes by region is which species to look for, which diseases to watch for in the weeks following a bite, and which seasons demand the most vigilance.
References
[1] CDC: Where Ticks Live
[2] CDC: Lyme Disease Surveillance Data
[3] Minnesota Department of Health: Tick-Borne Disease Statistics, 2024
[4] CDC: Tickborne Disease Surveillance Data Summary
[5] Northeast Regional Vector Center: Ticks of the Northeast
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