2001 vs 2014 maps showing areas ticks are found in

For many Americans, the ticks that transmit Lyme disease have replaced mosquitoes as summertime enemy number one.

Janet Foley is a professor who studies infectious diseases at the University of California, Davis.

Foley: “I grew up in Maine, and when I was a kid there were no deer ticks ever. And Maine arguably has the worst epidemic in the United States right now of Lyme disease.”

The problem is not just in Maine. Annual reported cases of Lyme disease in the U.S. have more than doubled over the past 20 years. Foley says part of the reason is that warmer winter temperatures have allowed the ticks to thrive in new areas, so more cases are now reported in places like upstate New York, and the upper Great Lakes region.

Foley: “The expansion north is certainly associated with climate change.”

And it’s not just rising temperatures. Changes in precipitation, humidity, and vegetation can also affect tick populations and the transmission of Lyme disease.

Foley: “We’re going to have to expect disease – whether Lyme disease or other diseases – to be a constant emerging problem that we have to deal with.”

As the risks increase, she says it’s more important than ever for people all over the country to learn how to prevent and treat tick-borne diseases.

Reporting credit: Sarah Kennedy/ChavoBart Digital Media.
Image graphic: Created by David McCarthy. Maps source: CDC Data and Statistics

Diana Madson contributed regularly to Yale Climate Connections from 2014 to 2021. She enjoys exploring U.S.-based stories about unexpected and innovative solutions to climate change. In addition to her...