One sign that 2017 will be a bad year for Lyme disease

Lyme disease is caused by the bacterium Borrelia burgdorferi and is transmitted to humans through the bite of infected blacklegged ticks.

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An explosion in the mice population across the northeastern United States is a worrying sign of a potentially similar-sized surge in cases of Lyme disease.

But people get Lyme disease from ticks, not mice, right?

Deer are often blamed for being carriers of Lyme disease, infecting the ticks who feed on them, who then jump on to human hosts. But mice are among the most effective carriers of the condition, infecting 95 percent of the ticks who feed on them, according to NPR.

Two biologists told NPR that they have found in mice a leading indicator of future Lyme outbreaks: the bigger the annual mouse population, the larger the following year's pool of new Lyme cases will be.

Once found primarily in the New England (the disease is named for Lyme, Connecticut), and a slice of Wisconsin, Lyme is now found all over the United States.

Its rise results in part from rising deer populations, but also in the changing landscape of the country. Land development for farming, housing and commerce has chewed through the once vast forests and wild lands of the U.S., leaving smaller patches of forest interspersed with human settlements. Mice thrive in these smaller forests, in large part because the larger animals who prey on them cannot.

Reported cases of Lyme have tripled since the 1990s to 30,000 a year, but health officials think the real number could be ten times that, noted NPR.