Rising Temperatures May Push Lyme Disease Risk Westward in Maryland

A mathematical model developed by UMD researchers illustrates how Lyme-carrying ticks respond to shifting temperatures, redistributing disease risk across the state.

As surface temperatures rise and reshape ecosystems across the United States, a new study suggests that Lyme disease—one of the country's most common vector-borne illnesses—may not just spread but relocate.

University of Maryland researchers found that rising temperatures are likely to shift Lyme disease risk westward in Maryland, reducing transmission in some densely populated regions while increasing it in cooler, less-populated areas.

Published in the journal Royal Society Open Science on March 25, 2026, the researchers developed a detailed mechanistic mathematical model calibrated with two decades of ecological and case data to simulate how warming affects the lifecycle of the black-legged tick, Ixodes scapularis, the primary vector of the Lyme-causing bacterium Borrelia burgdorferi.

“Vector-borne diseases constitute about 16% of all infectious diseases of humans,” said the study’s senior author Abba Gumel, a Distinguished University Professor of Mathematics at UMD with a joint appointment in the University of Maryland Institute for Health Computing. Gumel also holds the Michael and Eugenia Brin Endowed Chair in Mathematics.

“This study helps answer a central question in ecology, whether and how anthropogenic climate change will alter these diseases’ distribution and burden,” he said.

A moving target

Scientists have long known that temperature plays a crucial role in tick development, survival and host-seeking activity. The new paper highlights a nuanced reality: ticks and Lyme disease transmission intensity peak within a narrow thermal band—17 to 20.5 degrees Celsius (roughly 63 to 69 degrees Fahrenheit). Outside that range, tick survival and transmission capacity decline.

As surface temperatures rise, that optimal “sweet spot” is expected to shift downward.

The researchers found that under moderate warming scenarios, parts of central Maryland, currently the hardest hit by Lyme, could see a decline in disease risk as temperatures rise above the range optimal for tick activity. Meanwhile, cooler western counties, including mountainous regions with historically few Lyme cases, may warm into the new optimal range, becoming more vulnerable to sustained transmission.

With more extreme warming, the shift becomes even more pronounced. 

“Under the high-emission scenario, Western Maryland falls fully within the new temperature window and emerges as the primary hot spot, while central, southern and eastern counties, where about 70% of the state’s population live, experience significant reductions in transmission due to thermal overshoot,” said study co-author Salihu Musa, a visiting assistant research scientist at UM-IHC. 

Importantly, the net effect of both warming scenarios is a statewide reduction in overall Lyme disease burden—but with the emergence of new risk areas in less populated western counties, the authors noted.

A patchwork future

The findings challenge a common assumption.

“Global warming does not uniformly intensify Lyme disease risk,” Gumel said. “Instead, it shifts the thermal landscape.” 

The resulting redistribution of risk creates a patchwork that could complicate public health planning, he said. But that planning is essential, as Lyme disease is unlikely to disappear on its own even without shifting weather patterns.

“Our theoretical analysis establishes that under current ecological and environmental conditions, Maryland will continue to experience Lyme disease outbreaks,” Gumel said. 

Rising temperatures only underscore the need for intervention. And no single intervention will do the trick, the authors said.

“A hybrid strategy combining rodent baiting, habitat clearance and personal protection offers the most robust pathway to elimination,” Musa said. “At moderate coverage levels—­­around 50%—this integrated approach remains effective under both moderate and high warming scenarios.”

He added that “elimination of Lyme disease in Maryland is mathematically feasible, but the threshold for intervention success rises with temperature.”

The study's authors emphasized that their mechanistic modeling framework intentionally focuses on temperature as the central climatic driver, enabling a clear, data-driven understanding of how rising temperatures reshape tick ecology and disease distribution. This approach provides public health officials with a powerful, interpretable tool for anticipating geographic shifts in risk and designing adaptive intervention strategies across Maryland.