Last summer, in a town just outside New York City, a tick bit a man.

This ought to sound unexceptional. Ticks are normal on the upper East Coast; after all, tick-transmitted Lyme disease was first identified next door, in Connecticut. But the tick that covertly slid its pointy barbed mouthparts into an unlucky 66-year-old Yonkers resident was something new. It was the first invasive tick to arrive in the United States in 50 years, and this was the first time it had bitten a human.

Maryn McKenna (@marynmck) is an Ideas contributor for WIRED, a senior fellow at the Schuster Institute for Investigative Journalism at Brandeis University, and the author of Big Chicken.

That bite didn’t make its victim sick. But that it occurred at all is causing scientists to realize how little they know about the insect involved, known as the Asian longhorned tick: what diseases it transmits, where it prefers to live, and how it manages to move across long distances. Behind those unanswered questions looms a larger problem: We haven’t paid as much attention to ticks as we have to other insects that carry diseases. We have a long way to go to catch up—just as changes in weather patterns have ticks on the move too.

Until recently, the Asian longhorned tick’s home range was understood to be eastern China and Russia, Japan, Australia and New Zealand, and a few Pacific islands. In those countries, it harbors an array of bacterial and viral diseases that infect humans, including a potentially deadly hemorrhagic fever. It’s even more feared for the way it attacks livestock. This tick reproduces asexually, laying thousands of eggs at a time and producing waves of offspring that extract so much blood that grown cattle grow weak and calves die.

In August 2017, a woman who kept a single sheep on a property in the northwest corner of New Jersey, in the midst of a neighborhood of big houses and big lawns, walked into the Hunterdon County health department to complain that she had found ticks on the animal. What she didn’t realize, until horrified employees told her, was that she had ticks on herself as well, more than 1,000 speck-sized larvae all over her clothing.

The investigators gave the woman a spare set of pants and went back to her house with her—where their boots were immediately covered with crawling larvae, many times more than would be normal on a property that size. They found hundreds of ticks sucking on the ears and under the coat of her poor sheep.

An insecticide bath took care of the bugs on the sheep, and a hard freeze in November eliminated the ones in the paddock. By that time, Rutgers University researchers had identified it as the longhorned tick, confirming the bug’s first sighting outside of a quarantine station (where twice in the 1960s they were removed from animals being brought into the United States). They had no idea where it had come from, but they wondered: Given that the paddock was so populated, how long had the ticks been here? Was it long enough that they might already be moving around?

Apparently yes. The CDC said last Wednesday the exotic tick has been found in 11 states now. One is New York, where the Yonkers man lives, about 80 miles away from that infested paddock. At the time of the bite, he didn’t travel much: He hadn’t been outside Westchester County in a month. He wasn’t all that outdoorsy either.

But when investigators inspected the man’s house they found ticks and tick larvae all around it. Unsettlingly, they also found ticks where existing science says ticks shouldn’t be: resting in full sun in the middle of a well-tended lawn, instead of in shaggy, shady tall grass.

The foreign tick had arrived without explanation, moved without notice, flourished in areas where it should not have been successful—and now was posing a possible human health threat.

The exotic Asian longhorned tick has been found in 11 states now.

“I’m alarmed,” says Bobbi Pritt, a physician and pathologist at the Mayo Clinic in Minnesota, who wrote a medical journal commentary reacting to the news of the bite, which was disclosed last month in a medical journal. “Though I’m not surprised. We knew this tick was here, we knew it had the capability of biting people based on its behavior in other countries. So now that raises a lot more questions.”