Lyme disease and other tick-borne diseases are growing in case numbers, some among areas where it used to be rare, according to a recent report from the U.S. Centers for Disease Control and Prevention.

The report shows a 25% increase in tick-borne diseases between 2011-2019, with notable increases in Vermont (1,602%), Maine (1,422%) and New Hampshire (372%).

Babesiosis, defined by the CDC as a tick-borne disease caused by parasites that infect red blood cells, is now considered endemic in these three states, said the report.

Confirmed cases of Lyme disease rose 44% from 1999-2019, per NBC News.

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Why the increase?

NBC News said researchers figure the cause for the rise in babesiosis and Lyme disease cases is due to increased traveling and home-building in forested areas, expanding deer populations and global warming.

NPR said, “In the Northeast, upper Midwest and northern Pacific Coast, the warming climate enables ticks to become active earlier in the spring and then remain active later into the autumn or winter months, extending the window of tick-borne disease risk each year.”

Edouard Vannier, an assistant professor who studies babesiosis at Tufts Medical Center in Boston, told NBC News, “The ticks are surviving better in the winter, and so the next spring, you have more ticks to bite more people.”

Dr. Peter Krause, a senior research scientist at the Yale School of Public Health, told NBC that older people are more vulnerable to babesiosis, making them more likely to get an official diagnosis for the disease.

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Symptoms and treatments

Symptoms for Lyme disease, per the CDC, can include “fever, chills, headache, fatigue, muscle and joint aches, and swollen lymph nodes,” accompanied by a rash that may appear three to 30 days after a tick bite.

Melissa Prusinski, research scientist and laboratory supervisor at the New York State Department of Health, told NPR that people often mistake Lyme disease symptoms for the flu or COVID-19.

“Not everybody has the rash,” Prusinski told the news outlet, adding that “sometimes the rash is in an area that you can’t easily see, like on the scalp.”

Krause told NBC that babesiosis has no defining feature or obvious symptom, and it’s usually diagnosed through a blood test.

The U.S. Food and Drug Administration said concerning a treatment for Lyme disease that antibiotics recommended by the person’s doctor before diagnostic tests are completed usually help people recover quickly.

The Association of American Medical Colleges said that a Lyme disease vaccine is yet to be approved, but has undergone testing, as of last year.