New research identifies 76 western U.S. counties with potentially suitable habitat for Lyme-infected ticks. Meanwhile, findings from North Carolina suggest the nation’s tick-borne disease landscape is changing.
For decades, Americans have associated Lyme disease with the wooded landscapes of New England, Pennsylvania, and the upper Midwest.
But a newly published scientific study is drawing attention to a less-recognized part of the country’s Lyme disease landscape: the Pacific Coast.
Researchers from the Centers for Disease Control and Prevention have identified dozens of western U.S. counties where environmental conditions may support ticks infected with the bacteria responsible for Lyme disease.
The findings, published October 11, 2026, in the scientific journal Parasites & Vectors, point to potentially suitable habitats across California, Oregon, and Washington.
And while the research focuses on the West, another recent investigation has uncovered concerning evidence of Lyme-carrying ticks much closer to home—in the mountains of North Carolina.
Together, these studies reinforce an important public health message: Lyme disease risk extends beyond the regions traditionally associated with the illness, and better surveillance is essential to understanding where people may be exposed.
Scientists Identify 76 Western Counties With Suitable Habitat
The western study, conducted by researchers James C. Burtis, Erik Foster, and Rebecca J. Eisen, examined tick surveillance records and environmental conditions across seven western states.
Their goal was not simply to determine where ticks live.
They wanted to identify areas capable of supporting western blacklegged ticks carrying Borrelia burgdorferi, the bacterium responsible for most Lyme disease infections in North America.
The distinction matters because not every tick carries the bacteria, and the presence of a tick species does not automatically mean significant local Lyme disease transmission.
Researchers reviewed surveillance records documenting the presence of host-seeking immature ticks, known as nymphs, and evidence of infected western blacklegged ticks.
They found:
- 54 counties with documented host-seeking western blacklegged tick nymphs.
- 36 counties with records of infected western blacklegged ticks in California, Oregon, and Washington.
- 76 counties classified by at least one habitat model as potentially suitable for infected, host-seeking nymphs.
A previous modeling effort had identified 113 counties with suitable habitat for western blacklegged ticks generally. The new work narrowed attention to conditions relevant to infected nymphs that could encounter people.
Importantly, these 76 counties were not newly confirmed human Lyme disease hotspots.
The models identified potential habitat; they did not calculate how likely a person was to become infected in any particular county.
Nevertheless, the findings offer public health agencies a more focused map for future tick surveillance.
Where Are the Western Lyme Disease Risk Areas?
The study identified suitable environments primarily in central and northern California, along with coastal portions of Oregon and Washington.
A separate October 16 report from LymeDisease.org highlighted several California regions with historically elevated Lyme disease incidence.
These include the northwestern coastal counties of Mendocino, Humboldt, and Trinity, parts of the northern Sierra Nevada foothills, and coastal and Bay Area counties such as Marin, Santa Cruz, Monterey, and Contra Costa.
The geographic pattern challenges the assumption that Lyme disease is primarily associated with the eastern United States.
California’s forests, wooded hillsides, and certain coastal environments can support the western blacklegged tick, scientifically known as Ixodes pacificus.
The species plays a role similar to the eastern blacklegged tick, Ixodes scapularis, in transmitting Lyme disease bacteria.
But there are important ecological differences between the two regions.
Tick populations, animal hosts, vegetation, weather, and the prevalence of infection all influence local transmission.
That means the presence of suitable habitat should not be confused with the level of danger faced by an individual hiker or homeowner.
A map showing where infected ticks might survive is not the same as a map showing how many people will become infected.
Why the Smallest Ticks Deserve Serious Attention
One of the study’s central concerns involves tick nymphs.
These immature ticks can be extremely small, making them difficult to notice on the skin.
Yet nymphs are responsible for a substantial share of human Lyme disease infections.
Ticks acquire Borrelia bacteria through their interactions with infected animal hosts. They can subsequently transmit the bacteria during feeding.
This makes the relationship between wildlife, ticks, environmental conditions, and human activity especially important.
A wooded trail may appear perfectly safe while still providing habitat for infected ticks.
And because a person may never notice the bite, identifying Lyme disease early can sometimes be challenging.
According to the CDC, early symptoms may include fever, fatigue, headache, muscle and joint aches, and an expanding rash called erythema migrans.
Contrary to popular belief, that rash does not always appear as a classic bull’s-eye pattern.
Symptoms can appear days or weeks after exposure.
When recognized and treated promptly, Lyme disease is generally responsive to recommended antibiotics. Delayed treatment can increase the risk of complications involving the joints, heart, or nervous system.
North Carolina Is Seeing Its Own Warning Signs
Although the new habitat study examines western states, North Carolina researchers have documented a different but equally important development.
In August 2026, the CDC published findings from a surveillance project in Biltmore Forest, a wooded community near Asheville.
The study was conducted by investigators affiliated with the University of North Carolina at Chapel Hill, North Carolina State University, the University of South Carolina, and the CDC.
Researchers collected 373 ticks from residential properties between November 2024 and August 2025.
Of those, 287 were blacklegged ticks.
Among 48 adult blacklegged ticks tested for Lyme disease bacteria, *19—or approximately 40%—were positive for Borrelia burgdorferi.*
Researchers also detected other tick-borne pathogens, including Borrelia miyamotoi and Anaplasma phagocytophilum.
These findings were striking because southern Appalachia has not historically been considered a major Lyme disease region on the scale of the Northeast.
However, the Biltmore Forest data represent a relatively small, localized sample. The 40% figure should not be interpreted as the infection rate for ticks throughout Asheville, western North Carolina, or the state.
The CDC report nevertheless concluded that enhanced surveillance, physician awareness, and public education are warranted.
For residents of Charlotte and the Piedmont who frequently travel to Boone, Asheville, and the Blue Ridge Mountains, the findings provide another reason to take tick prevention seriously.
America’s Lyme Disease Maps Are Improving
Why does better tick surveillance matter?
Because public health decisions depend on knowing where disease exposure is possible.
If an area is assumed to have little Lyme disease activity, patients and physicians may be less likely to consider Lyme disease when evaluating symptoms after potential tick exposure.
Conversely, exaggerated interpretations of risk can create unnecessary fear and inappropriate testing.
The solution is more precise information.
Modern tick surveillance increasingly combines field collection, molecular testing, geographical data, and environmental modeling.
Researchers can use these tools to identify regions where infected ticks have been collected, investigate where suitable habitat exists, and prioritize areas requiring additional monitoring.
But models must be validated against real-world findings.
Changes in tick distribution also cannot automatically be attributed to climate change alone. Land use, wildlife populations, habitat connectivity, human behavior, and surveillance practices can all influence what researchers observe.
The western study’s authors explicitly acknowledged that their models could not distinguish the magnitude of risk between counties.
That is precisely where additional field research becomes important.
Five Ways to Protect Yourself From Lyme Disease
Most people don’t need to avoid outdoor recreation because of tick-borne disease.
They need practical information and effective prevention strategies.
The CDC’s 2026 prevention guidance recommends several straightforward precautions.
1. Use Effective Tick Repellent
Choose an EPA-registered repellent containing ingredients such as DEET or picaridin, following the product instructions.
Clothing and outdoor gear can also be treated with 0.5% permethrin. Permethrin clothing treatments should not be applied directly to skin.
2. Perform Tick Checks After Outdoor Activities
Carefully inspect your body after hiking, gardening, camping, or spending time in brushy or wooded areas.
Pay particular attention to the scalp, behind the ears, under the arms, around the waist, behind the knees, and other concealed areas.
Check children and pets as well.
3. Remove Attached Ticks Immediately
Use fine-tipped tweezers to grasp the tick close to the skin and pull outward with steady, even pressure.
Avoid burning the tick or covering it with petroleum jelly or other substances.
Prompt removal helps reduce the likelihood of transmitting certain tick-borne infections.
4. Recognize Early Symptoms
Don’t wait for a classic bull’s-eye rash.
If you develop an expanding rash, unexplained fever, fatigue, or muscle and joint aches after potential tick exposure, contact a healthcare professional.
Describe where you have traveled and when exposure may have occurred.
5. Ask About Preventive Treatment When Appropriate
In certain circumstances, a healthcare professional may recommend a single preventive dose of doxycycline after a high-risk tick bite.
This is not necessary for every bite and depends on factors including tick identification, attachment duration, timing, and local disease risk.
The Future of Lyme Disease Prevention Starts With Better Information
Lyme disease remains a major public health concern, but its geographic distribution is more complicated than the familiar image of deer ticks in New England.
The latest research illustrates the value of looking beyond traditional disease maps.
In the West, scientists are identifying environments where infected ticks may be able to survive and encounter people.
In North Carolina, researchers are documenting evidence of infected tick populations in areas where Lyme disease historically received less attention.
Neither finding justifies panic.
Both justify continued research, improved surveillance, better physician education, and accessible prevention information.
As scientific tools improve, public health agencies have an opportunity to identify risk more precisely and help people seek appropriate treatment earlier.
The ultimate goal is not simply to make better maps of Lyme disease. It is to prevent infections, improve diagnosis, and reduce the burden of tick-borne illness on patients and families.
And that begins with understanding where the risks actually exist.
Sources: Burtis, Foster, and Eisen, Parasites & Vectors (October 2026); CDC Morbidity and Mortality Weekly Report (August 2026); LymeDisease.org (October 2026); CDC Lyme Disease Prevention Guidelines.
This article is provided for educational purposes and is not a substitute for professional medical advice.