A Rising Threat: Lyme Disease Cases Surge in the U.S. as Tick Populations Expand

Tick bites, a known hazard for hiking and camping enthusiasts, are becoming an increasing concern across the United States due to the diseases they can transmit, most notably Lyme disease. The U.S. Centers for Disease Control and Prevention (CDC) reported a significant rise in Lyme disease cases, with the numbers reaching 62,551 in 2022, nearly double the average of the previous decade which stood at about 33,000 cases annually.

Lyme disease, transmitted through tick bites, is the most commonly reported tick-borne illness in the U.S., and its diagnosis can be challenging. Although officially reported infections were close to 63,000 last year, the CDC estimates the actual number could be up to ten times higher due to underreporting and diagnostic difficulties.

The prevalence of Lyme disease varies significantly by state, with the northeastern, Midwest and Mid-Atlantic regions historically seeing higher rates of infection. However, climate change is altering this landscape by increasing temperatures, thereby expanding the habitats suitable for ticks and potentially increasing the risk of Lyme disease nationwide.

“Deer ticks are mostly active when temperatures are above 45 degrees Fahrenheit, and they thrive in areas with at least 85% humidity,” notes the U.S. Environmental Protection Agency. “Warming temperatures associated with climate change are projected to increase the range of suitable tick habitat.” This expansion means that annual cases of tick-borne diseases are expected to continue to rise as ticks invade new areas.

In high-risk areas, an estimated 10% to 50% of black-legged ticks carry the bacteria that causes Lyme.

These high-risk areas include:

• Eastern states, primarily New England and the mid-Atlantic.
• The Great Lakes Region and northern Midwestern states, especially Wisconsin and Minnesota
• West Coast, particularly parts of northern California and less commonly, Oregon and Washington

In 2022, Rhode Island, Vermont, and Maine reported the highest rates of Lyme disease, with Rhode Island topping the list at 212 cases per 100,000 people. Vermont and Maine followed closely with 204 and 194.7 cases per 100,000, respectively, according to the CDC.

Pennsylvania was particularly hard hit, with seven of the ten counties most affected by Lyme disease located in the state from 2016 to 2019. During this period, Pennsylvania accounted for nearly 30% of all reported Lyme disease cases, with New Jersey trailing at 12%, according to data from USAFacts.

How to stay safe from tick bites

The CDC and other public health experts recommend the following to keep you and your family safe from ticks

• When spending a significant time outdoors, treat clothing and gear with products that have .5% permethrin or buy such items already pre-treated with permethrin.
• Consider long pants and high socks in favor of shorts.
• Avoid high grass and leaf litter. On hikes, try to walk in the center of the trails.
• Inspect clothing and gear periodically for the presence of ticks.
• To learn how to properly remove a tick if it’s attached to skin, go here.

The black-legged tick and the Western black-legged tick are the primary vectors for the bacteria that cause Lyme disease. In high-risk areas, an estimated 10% to 50% of these ticks carry the bacteria, leading to a range of symptoms in affected individuals. Early-stage Lyme disease may present with a distinctive “bullseye” rash, fever, chills, fatigue, and muscle and joint aches. If left untreated, the disease can progress to more severe health issues, including neurological, heart, and joint problems.