Introduction
Lyme disease, caused by the bacterium Borrelia burgdorferi, is the most common tick-borne illness in the United States, Europe, and parts of Asia. Transmitted primarily by the blacklegged tick (also called the deer tick), the risk of infection is heavily influenced by geography.
Understanding where Lyme disease is most prevalent can help individuals, families, and pet owners take proactive steps to protect themselves. This article explores the global and regional spread of Lyme disease, with a special focus on high-risk areas, reasons for its expansion, and practical prevention strategies.
What Determines the Geographic Spread of Lyme Disease?
The spread of Lyme disease is primarily influenced by the habitat of ticks and their animal hosts. Factors include:
- Tick population density
- Presence of animal reservoirs (especially white-footed mice and deer)
- Climate and vegetation (ticks prefer humid, wooded, or grassy areas)
- Human activity in tick habitats
- Changes in land use and climate change
Global Overview: Where Lyme Disease Is Found
Lyme disease is reported across North America, Europe, and parts of Asia.
North America
- United States: High prevalence in the Northeast, Upper Midwest, and Pacific Northwest
- Canada: Increasing in southern Ontario, Quebec, Nova Scotia, and parts of Manitoba
- Mexico: Rare but cases reported near northern border regions
Europe
- Lyme is endemic across central, northern, and eastern Europe
- Highest rates in Germany, Austria, Slovenia, Czech Republic, Sweden, and Switzerland
- Also present in the UK, though less common
Asia
- Found in China, Russia, and Japan
- Caused by various species of Borrelia (e.g., B. garinii, B. afzelii)
High-Risk Regions in the United States
According to the CDC, over 90% of Lyme disease cases in the U.S. are reported from just 15 states.
Northeast
- Connecticut
- Massachusetts
- Rhode Island
- New York
- New Jersey
- Pennsylvania
- Maryland
Why high risk? Dense woods, abundant deer and small mammals, humid climate—ideal tick environment.
Upper Midwest
- Wisconsin
- Minnesota
- Michigan
Why high risk? Forested areas with large tick populations and active outdoor lifestyles.
Mid-Atlantic and Appalachians
- Virginia
- Delaware
- West Virginia
Expanding into North Carolina and Kentucky in recent years due to climate shifts.
West Coast
- Northern California
- Oregon
- Washington State
Here, the western blacklegged tick (Ixodes pacificus) carries Lyme, but risk is lower and more localized.
Why Is Lyme Disease Spreading?
Lyme disease has become more widespread over the past two decades. Reasons include:
- Suburban development into wooded areas
- Deer population growth (main tick host)
- Warmer winters allowing ticks to survive longer
- Increased outdoor activity (hiking, gardening)
- Better awareness and reporting
Ticks are also being found in new geographic areas, including higher elevations and northern regions previously considered low risk.
Lyme Disease in Pets and Wildlife
- Dogs are frequently affected in endemic areas.
- Wildlife like deer, mice, birds, and squirrels serve as hosts for ticks and help expand the range.
- Birds, in particular, can transport ticks over long distances, introducing them to new areas.
Mapping Risk: Tick Surveillance and Reporting
The CDC and other public health agencies maintain Lyme disease case maps based on human and tick surveillance data. These help identify:
- Endemic counties (where Lyme is consistently reported)
- Emerging areas with rising case numbers
- Safe zones with little or no tick presence (e.g., much of the South and Southwest U.S.)
You can check local tick risk using the TickEncounter Resource Center or the CDC’s Lyme maps.
Preventing Lyme Disease in High-Risk Areas
If you live in or travel to a high-risk region, take these precautions:
Personal Protection
- Use EPA-approved tick repellents (e.g., DEET, picaridin)
- Wear long sleeves and pants, tuck pants into socks
- Treat clothes with permethrin
- Stay on trails, avoid tall grass and leaf litter
Tick Checks
- Check yourself, kids, and pets daily, especially after outdoor time
- Pay close attention to scalp, behind ears, under arms, groin, and ankles
Property Management
- Keep grass mowed
- Remove brush piles and wood debris
- Create tick-safe zones with gravel or woodchip barriers
Protect Pets
- Use veterinarian-recommended tick preventives
- Consider Lyme vaccination if your dog lives in a high-risk area
Conclusion
Lyme disease is a geographically influenced illness—where you live, hike, or vacation significantly affects your risk. Staying informed about high-risk regions, monitoring tick activity, and following prevention guidelines are crucial steps in protecting yourself, your family, and your pets.
Whether you’re a lifelong resident of New England or planning a camping trip to the Midwest, awareness of Lyme’s geographic spread empowers you to take smart precautions and stay healthy.
FAQs:
Where is Lyme disease most common in the U.S.?
Primarily in the Northeast, Upper Midwest, and parts of the West Coast.
Is Lyme disease spreading to new areas?
Yes, due to climate change, land development, and tick migration, Lyme is expanding into southern and northern U.S. regions.
Are ticks active all year round?
Ticks are most active from spring through fall, but in warmer regions, they can be active year-round.
Can I get Lyme disease in urban areas?
Yes, especially in suburban neighborhoods near woods. Ticks thrive in backyards with deer or rodents.
How do I know if my area is high risk?
Check CDC maps, contact your local health department, or use online tools like TickEncounter.org.
