There’s a new type of Lyme disease in New York state.
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Almost all cases of the tick-borne illness in the United States are caused by corkscrew-shaped bacteria called Borrelia burgdorferi. But B. burgdorferi is actually one of two Lyme disease-causing species in the U.S. The other, Borrelia mayonii, is far more rare. Until now, it has only ever been detected in Minnesota and Wisconsin. Both types of bacteria are spread by deer ticks.
According to a Centers for Disease Control and Prevention report published Thursday, a case of B. mayonii Lyme disease was detected in upstate New York last July.
The novel infection occurred in an adult living in Herkimer County, which stretches from the edge of Utica into the Adirondack Mountains. The individual hadn’t recently traveled, according to the report.
The state health department found a handful of ticks on the person’s wooded property that tested positive for the bacteria. But a much wider search, of more than 1,500 ticks from 24 New York counties, didn’t find the bacteria again.
It’s unclear exactly how the bacteria made their way to Herkimer County.
“While this finding was unexpected, we do know that a range of ticks and tick-borne disease can change geographically over time,” a spokesperson from the New York State Health Department said in an email.
Douglas Norris, a professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health in Baltimore, said that the bacteria has likely been present in New York ticks for a couple of years, though it appears to be contained to a very small area.
Same disease, different symptoms
Researchers know much less about B. mayonii than they do about B. burgdorferi. There have been far fewer infections from the former to study, and the bacteria was only discovered by Rochester, Minnesota-based Mayo Clinic researchers in 2016 –– 35 years after B. burgdorferi. Both species can cause debilitating disease.
Both infections can begin with a fever and headache, but Lyme disease caused by B. mayonii is more likely to cause nausea and vomiting.
People infected with the less common species may also forgo the diseases’ hallmark bullseye rash that surrounds the tick bite, Norris said. Instead, they may have a more widespread rash, which could look like tiny red spots over a part of their body, rather than just over the bite.
“People also have more neurological symptoms,” said Dr. Bobbi Pritt, a pathologist at the Mayo Clinic. Pritt was one of the scientists who discovered the B. mayonii bacteria. “There could be more broad symptoms that we haven’t seen yet.”
The health department would not disclose what symptoms the New Yorker infected with B. mayonii last year had.
Rising cases of Lyme disease
Lyme disease cases have skyrocketed across the Northeast in recent years. Between 2020 and 2024, the incidence of Lyme disease in New York state increased by nearly 450%, from about 37 cases per 100,000 people in 2020 to nearly 165 cases per 100,000 in 2024, health department statistics show.
Although more B. mayonii cases are likely to show up throughout the Northeast, these infections are expected to remain rare, Pritt said.
“I think Borrelia burgdorferi will remain the most common form of Lyme in the U.S., we know Borrelia mayonii is not the primary cause of Lyme disease to start with,” she said.
Even in the upper Midwest, where B. mayonii have been detected in the past , the bacteria causes a minority of Lyme disease cases. B. mayonii only causes about two of the nearly 3,000 cases of Lyme disease cases detected in Minnesota every year, according to the Minnesota Department of Health.
Just 0.2% of nymphs, or young ticks, collected throughout New York carried B. mayonii, compared to about 1% of adult ticks, the health department found. On the other hand, B. burgdorferi infects about one-quarter of nymphs in the Northeast and half of all adult ticks.
Ticks have to be attached to a person for 24 to 48 hours before they can pass on infectious bacteria, so stealth is key. For this reason, nymphs, which are about the size of a poppy seed, are typically the ticks that spread Lyme disease, Norris said.
“A big tick a human will usually notice, but those little guys not so much,” Norris said.
Climate change expanding Lyme disease ‘sweet spot’
Climate change is reshaping where tick-borne disease spreads, though it is not likely to be the cause of B. mayonni showing up in New York, Norris said.
“Unfortunately it got introduced into the sweet spot,” he said.
Experts don’t know how the bacteria got there, but Norris said it’s possible that an infected tick may have hitched a ride on a bird that migrated to New York from Minnesota or Wisconsin.
New York and the broader Northeast region of the U.S. have ideal weather for ticks to incubate the bacteria that cause Lyme disease to a point where it can infect people. This so-called sweet spot is shifting north because of climate change, to Maine and southern Canada, causing more widespread Lyme disease and skyrocketing cases in places like New York, where Lyme disease has been known to circulate for decades.
Pritt said that, to prevent tick bites, people should stay in the middle of trails while hiking to avoid contact with taller grasses that can harbor ticks. When possible, people should wear long sleeves and tuck pants into socks to try to keep bugs from latching onto skin, she said. Pritt also recommends using 30% DEET or oil of lemon eucalyptus bug repellant. Checking yourself and your pets for ticks every hour or so when in tick territory is also a good idea. So is showering and doing a thorough tick check once you’re back home.
“We don’t want people to be afraid of the outdoors,” she said. “But ticks can transfer a whole host of things, other parasitic and viral diseases, so the bottom line is that people need to protect themselves from tick bites.”