The state’s altered forests

into adulthood. Only 15% of nymphs (young ticks) that the team collected carry Lyme, but within a year of feeding on mice that carry the disease, almost half adult ticks carry Lyme disease. Nymphs are a threat to humans because they are so small and their bites often go undetected.

The town of Lyme, of course, is like ground zero for Lyme disease, which was discovered there in the 1970s. The blacklegged ticks carry Lyme disease and four other deadly diseases: anaplasmosis, borrelia miyamotoi disease, babesiosis, and Powassan virus.

Williams said infection with Powassan in 2019 was low, just five cases in the state. But Powassan is a dangerous illness. Former U.S. Sen. Kay Hagen of North Carolina died of Powassan in October. Congress is considering a bill called the Kay Hagan Tick Act for tickborne disease research funding.

Lyme disease has become a national health crisis. It is caused by a microscopic spirochete that enters the bloodstream and hides in the tissues. In 2018, Connecticut ranked fourth in the nation for Lyme cases, with 1,859 reported new cases that year, the Centers for Disease Control and Prevention (CDC) said. But the actual cases are probably 10 times that number (or roughly 18,500), the CDC reported.

Nationwide, the CDC estimates 300,000 cases a year. In 2015, a study at Johns Hopkins University estimated that as many as 440,000 new cases of Lyme are diagnosed each year, costing the health system $712 million to $1.3 billion a year.

Lyme disease has been around for millennia. It evolved into ticks that bite humans because the landscape now favors those ticks.

Since about 1900 Connecticut has changed from mostly farmland into a land of small forest patches interrupted by grassy areas. The white-tailed deer and white-footed mouse, two important animals whose blood ticks need to survive, all thrive here.

Although 60% of Connecticut is forest, much of that forested land is cut up into narrow segments. Such fragmented woods create lots of places at the edge of woods where sunlight encourages the shrubs that deer eat—and where ticks survive.

At a forum on urban forests three months ago, Williams told a group of scientists and amateurs that deer have created landscapes that favor ticks. They eat native plants and leave behind invasive

This story was reported under a partnership with the Connecticut Health I-Team, a nonprofit news organization dedicate to health reporting.