Warmer Winters Are Fueling a Surge in Tick-Borne Illnesses

Tick-borne illnesses like Lyme disease are on the rise across the Northeast, fueled by shifting seasonal patterns and warming temperatures. As winters become shorter and milder, blacklegged ticks (commonly known as deer ticks) are staying active well beyond traditional risk windows, posing an extended public health threat to people in affected areas.

Andrew Lover, MPH, PhD, MS, deputy director of the New England Center of Excellence in Vector-Borne Diseases, says the lengthening of tick season is one of the most striking developments in recent years.

"The tick season is changing a lot in terms of the winters are less cold and potentially shorter, so ticks are active later in the fall and earlier in the spring than they have been historically," Lover said. "That really changes where people's risk perception should be. Not everyone thinks about ticks at Thanksgiving time here in the Northeast, but they're still active."

This extended activity is compounded by geographic expansion. Ticks are now becoming more prevalent in northern states like Vermont, New Hampshire, and Maine, regions that historically saw only sparse tick populations.

"The ticks are also spreading north through Vermont and New Hampshire and Maine, which historically had really small numbers in just a few isolated places for deer ticks, blacklegged ticks," Lover explained. "So the health systems in those three states are having to work really hard to start ramping up to deal with those health problems."

Tracking tick-borne disease incidence presents its own set of challenges. According to Lover, widespread presumptive treatment for Lyme—administering antibiotics based on symptoms or tick exposure alone—can obscure data and trends.

"One of the challenges, at least here in New England, is that at least Lyme disease is so common that there's a lot of presumptive treatment," he said. "So even without a diagnosis, people just get doxycycline if they have an attached tick. It's good for the patient level, but in terms of tracking health trends, it makes it a bit challenging."

Despite these difficulties, several promising prevention tools are in development. A resurgence of interest in Lyme vaccination is underway, and researchers are also testing passive immunization strategies.

"There’s a reinvigoration of that space to get a new or improved vaccine," said Lover. "And there's also some work trying to get some monoclonal antibodies, so you can get an injection at the start of the season which would really knock down the chances of Lyme disease."

He emphasized the continued importance of everyday prevention methods like EPA-approved repellents and frequent tick checks but noted that broader insights into exposure patterns may help target education efforts more effectively.

"There’s a lot of other work trying to understand exactly where people are getting most of their exposures, whether it’s around your house where you’re gardening or whether it’s during recreation," he said. "That will help to help people understand when they are at their highest risk and then take appropriate action."

As ticks continue to expand into new areas, even beyond the Northeast, researchers are keeping a close watch.

"Certainly the Upper Midwest has started to see more tick-borne disease in the last 20 years," Lover said. "Canada is also having some new places pop up. That’s just a general trend everywhere."

Yet one of the most critical and overlooked gaps in the fight against tick-borne illness lies in human behavior.

"A lot of people know they probably should use repellent and that long pants are a good idea, but it's challenging to do that every day whenever you're outside," Lover explained. "So I think that's really the big gap, trying to understand what types of interventions are easy to do, easy to remember, and work with people's lives on a day-to-day basis."