Lyme disease is not only becoming more rampant in its normal hotspot of the northeast United States, it’s spreading across the country, a new report from the Centers for Disease Control and Prevention warns.

“Over time, the number of counties identified as having high incidence of Lyme disease in the northeastern states increased more than 320 percent,” researchers write in the report. They also note that the disease is appearing in states where its never been recorded before.

One big reason why Lyme disease is spiking, according to the CDC report: climate change.

Ticks tend to live in densely-forested areas and are preyed on by white mice. But forest clearing has killed off many mice, leaving ticks without a predator to keep them in check. With humans crossing this terrain, it means ticks have a fresh crop of victims to attack. And thanks to warmer temperatures, ticks are spreading their terrain into America’s heartland from their normal stronghold on the East coast.

Lyme disease is an infection caused by the Borrelia burgdorferi bacteria found on blacklegged deer ticks. The disease was identified in 1975. Symptoms include a high fever, headaches, fatigue, and a skin rash. If untreated, the infection can spread to joints, the heart and nervous system. In some instances, Lyme disease can be fatal.

New Jersey is typically considered the capital of Lyme disease in America, but it’s spreading across the Mid-Atlantic to the Midwest, with high-risk counties in Connecticut, Massachusetts, New Hampshire, Maine, Vermont, Pennsylvania, Virginia, New York, Iowa, Michigan, and Minnesota.

Click here to see what to do to prevent yourself against Lyme disease—and what to do if you have it.

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Write to Tanya Basu at tanya.basu@time.com.