Why Lyme Disease?

Understanding the expanding threat of tick-borne illness

The CDC estimates that ~476,000 people may be diagnosed and treated for Lyme disease each year in the United States

Higher Incidence Rates

↑ 340.9%

Incidence increase since 1996

High Incidence States

States with endemic Lyme

Geographic Expansion

↑ 87.1%

County increase since 2001

Climate Impact

Rising

Warming temps extend tick season

Source: CDC (2025)

About This Dashboard

This interactive dashboard explores the relationship between climate change and the expanding geographic distribution of Lyme disease in the United States.

Lyme Disease 101: Learn about transmission, symptoms, and treatment
Geographic Distribution: Visualize cases across states and time
Climate & Risk Factors: Understand environmental drivers
Public Health Impact: Examine implications for healthcare systems

Navigate using the tabs above to explore each topic in detail

Key Findings

Rising Incidence: Lyme disease is the most common vector-borne illness in the US, with cases increasing dramatically over the past three decades.

Geographic Expansion: Blacklegged ticks are spreading northward and westward, bringing Lyme disease to previously unaffected regions.

Climate Connection: Warmer temperatures and changing precipitation patterns are creating favorable conditions for tick populations.

What is Lyme Disease?

Understanding America's most common vector-borne disease

Lyme disease is a bacterial disease transmitted by the bite of an infected tick. The primary bacterium that causes Lyme disease is Borrelia burgdorferi

How is Lyme Disease Transmitted?

Tick Species: In the eastern United States, black-legged ticks (sometimes called deer ticks) are the main species carrying the Borrelia bacteria, while along the West Coast of the United States, western black-legged ticks are the dominant species.

Habitats: Both species of ticks are most commonly found in grass (especially taller grass), brushy, and wooded areas. Areas with leaf litter may also harbors ticks.

Prevalence: Infection rates of the Borrelia bacteria in tick populations range from 0% to 50%. Both nymphal and adult ticks may be infected.

Risk Factors:

Spending time in wooded or grassy areas
Not using tick repellent
Not performing tick checks after outdoor activities
Living in or visiting endemic areas

Black-legged or Deer Tick (Ixodes scapularis) life stages

Transmission Time: Ticks must be attached to the host's skin (person or animal) for at least 24 hours to transmit the Borrelia bacteria.

Sources: CDC (2024); ALDF (n.d.)

Symptoms of Lyme Disease

Classic Sign: Up to 80% of cases present with a red Erythema migrans (EM) rash starting at the tick bite and expanding over time. It often develops a 'bulls eye' appearance with a concentric ring of rash around the smaller initial rash. This typically appears between 7 and 30 days after the bite.

Early Symptoms (3 – 30 days after bite):

Headache
Fatigue
Muscle and joint aches
Fever
Swollen lymph nodes

If Left Untreated: Neurological and cardiac symptoms may develop

Facial palsy
Arthritis and joint swelling
Irregular heartbeat or heart palpitations
Shortness of breath
Nerve pain
Brain or spinal cord inflammation

Sources: CDC (2024)

Treatment

What to Do If You Find an Attached Tick

After Time Outside

Remove the tick promptly: Carefully remove the tick with tweezers, grasping the tick as close to the skin as possible and pulling firmly and steadily outward.
Exposure less than 24 hours: Not all ticks are infected, and transmission of Borrelia bacteria is unlikely. Monitor for symptoms over the next 30 days.
Exposure more than 24 hours: First-line treatment is usually a course of doxycycline (an antibiotic) as prescribed by a healthcare provider. The person may also choose to watch and wait for symptoms and then begin treatment once symptomatic, especially if located in an area where Lyme disease is less common. Antibiotics are generally helpful when started within 10-14 days of the bite.
Testing for Lyme disease: Certain lab tests can detect antibodies to the Borrelia bacteria 4–6 weeks after exposure. Testing too early may result in a false negative because antibodies have not yet built up.

Sources: CDC (2024); Cornell Health (n.d.); Johns Hopkins (n.d.)

Long-term Consequences

Early diagnosis and treatment are crucial for best outcomes

Prompt Treatment: If Lyme disease is treated promptly with appropriate antibiotics, it usually resolves in a few weeks with no long-term consequences.

Delayed or No Treatment: Can lead to long-term nervous system and/or joint damage. Persistent symptoms in persons with Lyme disease are now called Post-Treatment Lyme Disease Syndrome to better describe ongoing consequences.

No Immunity: Another bite by an infected tick can re-transmit Lyme disease, even after recovery.

Sources: CDC (2025)

Where Does Lyme Disease Occur?

Visualizing the spread of Lyme disease across the United States

Sources: CDC (2025), U.S. Census Bureau (2025)

Regional Patterns

Northeast: Traditional endemic region; highest incidence.

Upper Midwest: Rapid expansion observed in recent years.

South & West: New cases appearing in previously unaffected areas.

Geographic Expansion

Northward expansion from traditional endemic areas
Emergence in previously non-endemic Midwestern states
Coastal regions show highest concentration
Western states reporting first confirmed cases

Source: CDC (2025)

Geography of Interest:

Geography Level:

Select Year:

Climate & Enviromental Risk Factors

Understanding how climate and environmental changes are expanding the population of people at risk for Lyme disease

A large expansion in the spatial distribution and concentration of Lyme disease cases is apparent from the data shown on the Geographic Distribution tab. Although case definitions have changed over time, that does not adequately explain the geographic expansion. There are several potential causes of this spread

Warmer Annual Temperatures

Extends tick active season and expands geographic range northward

Precipitation Changes

Wetter conditions in the central and northeastern U.S create favorable tick habitats

Milder Winters

Increases tick survival rates through warmer winter months

Outdoor Exposures

Likelihood of a tick encounter increases as Americans spend more time outdoors

Milder Winters

The major climate factor driving the increase of Lyme disease is the warming of wintertime temperatures. Deer ticks cannot survive over the winter when low temperatures are consistently colder than about 10°F. Historically, the northeastern United States regularly reached temperatures of that level, so tick populations were significantly reduced in most winters. Over the last few decades, rising wintertime temperatures now allow tick populations to survive.

These trends mean more people in more places are at risk for Lyme disease, underscoring the need for increased public health awareness and prevention.

Sources: NOAA NCEI (n.d.)

Public Health Implications

Understanding the public health implications of a wider geographic distribution of Lyme disease

Healthcare & Economic Burden

With larger numbers of people being exposed to ticks potentially carrying the bacteria, Lyme disease rates are likely to continue increasing. The cost to society is potentially quite large: in 2016 US dollars, the mean treatment cost was $1,200 for a case (median $240). For cases that become chronic, costs increase substantially. The estimated range of costs due to Lyme disease is $345–968 million USD (2016 US dollars).

Prevention & Early Action

Clear public health messaging on how to prevent tick bites
Guidance on how to handle a tick if a bite does occur
Education on the signs of Lyme disease to support early treatment

Mean Treatment Cost

$1,200

Per case (2016 USD)

Median Treatment Cost

$240

Per case (2016 USD)

Annual US Cost

$345–968M

Estimated total cost (2016 USD)

Source: Hook (2022)