Lyme disease cases again set a new record in Maine this year, as the tickborne illness continues to spread and intensify, especially in the mid-coast and Down East regions.

Lyme rates in those regions are three times higher than the statewide average and have roughly tripled over the past decade.

The number of Lyme infections statewide stood at 3,035 on Dec. 3. That exceeds the total for 2023, which was the highest year on record with 2,943 cases. More cases will be added to this year’s total in the final weeks of December, although Lyme cases tend to slow down in the winter months as ticks are less active.

Much of the increase in Lyme cases in recent years has come Knox, Lincoln, Hancock and Waldo counties, while the rates have increased more gradually in the southern and interior counties, according to Maine Centers for Disease Control and Prevention data.

Scientists are not sure why Midcoast and Down East Maine have seen rapidly rising rates of Lyme disease, which is caused by a bacterial infection from the bite of a deer tick. Lyme is the most common tickborne illness, although Maine has also experienced increases in other tickborne diseases, such as anaplasmosis and babesiosis.

“The Midcoast has really become the epicenter of tick abundance,” said Griffin Dill, integrated pest management specialist at the University of Maine Cooperative Extension’s ‘tick lab.’ “We’ve seen a shift in the focal point from Cumberland and York counties to the mid-coast range, where we’ve seen a drastic increase in tick density and corresponding human infections. We’re seeing ticks move further and further Down East.”

Indeed, the statewide average of Lyme case rates increased from 106 per 100,000 population in 2014 to 228.2 in 2024, slightly more than doubling. But many Midcoast counties have experienced a tripling of rates or more.

Waldo County, for instance, had a rate of 125.5 Lyme cases per 100,000 population in 2014, and a rate of 579 in 2024. In 2023, the rates were even higher, at 636.2. Knox went from 267.2 in 2014 to 675.3 in 2024.

And Washington County’s rates highlight the extent to which the range of the deer tick has expanded Down East, going from a rate of 44 cases per 100,000 in 2014, less than half the statewide average, to 292.6 in 2024, well above the state average.

Cumberland County, Maine’s most populous, meanwhile, has experience a much more gradual increase in rates, from 117.8 in 2014 to 124.6 in 2024. York County’s numbers have also increased slowly, going from 135.5 in 2014 to 125.5 in 2024, with a rate of 152.7 in 2023.

Interior and western counties have seen substantial increases as well, with Oxford County going from a rate of 75.1 in 2014 to 203.4 in 2024. Only Aroostook County has bucked the trend, with rates remaining close to zero for the entire 10-year period.

Dill said the spike in the Midcoast remains a mystery. Midcoast and Down East have coastal climates that are hospitable to ticks, with wet, humid weather and winters that don’t get as cold as the interior. But southern coastal Maine also has near-ideal habitat for ticks, and the region has not seen the same explosion in cases over the past 10-20 years.

“We don’t have a good reason,” Dill said. “The Midoast is perfect for tick proliferation, but why it’s directly translating to these really significantly higher case rates is a question that’s still trying to be figured out.”

Dill said it’s possible people in southern Maine have been taking tick precautions since the 1980s and 1990s and are better at avoiding tick bites.

Morgan Porter, public health educator at the Maine CDC, said it’s unclear why the Midcoast is such a hot spot for Lyme, but people who live in the region may be more likely to be in wooded areas or other tick habitats compared to residents of southern Maine.

“We really don’t have any slam dunk answers on why this is happening in the Midcoast and Down East,” Porter said. “We do know that right along the coast it’s a more constant mild climate, ideal from the perspective of a tick.”

Overall, climate change is contributing to increases in deer tick populations and the tick’s ever-extending range, Porter said.

“We’ve had some really mild winters recently,” Porter said. “With temperatures generally warmer, that helps the ticks get a running start into spring.”

Lyme disease is a year-round threat and ticks can still be active enough in the winter to spread the disease.

“When we get a nice February thaw, the ticks come out and are looking for a host,” Porter said.

Dill said extended warm weather in autumn is also likely a contributing factor in more Lyme cases, as people are outside more in the fall while ticks are more active. The University of Maine is researching how climate conditions affect tick survivability, and has set up 15 sites across Maine to measure tick density, soil temperature, soil moisture, air humidity, wildlife presence and other factors.

Symptoms of Lyme disease include a rash, although not everyone who contracts Lyme will develop a rash. Other symptoms could include joint pain, achiness, headache, fever, fatigue and swollen lymph nodes. A tick typically has to be attached for more than 24 hours before transmitting Lyme disease, according to the U.S. CDC.

Treatment is a course of antibiotics, but it’s important to diagnose as quickly as possible.

Angéle Rice of Bath contracted Lyme disease many years ago, and she suffered from long-term symptoms. About 5% to 20% of Lyme cases can result in chronic symptoms that can last years. MaineHealth is participating in a national study about chronic Lyme.

Rice said Mainers should realize they are living in “Tickville” and take precautions.

“If you live in Maine you should have it in the forefront of your brain that the ticks are here year-round,” said Rice, who was one of the leaders of the now-defunct Mid-Coast Lyme Disease Support and Education advocacy group.

To minimize exposure to ticks, wear long sleeves and pants when hiking, use tick repellant, remove leaves and brush from your property and be careful when handling wood. Shower when returning from extended time in tick habitat, and perform frequent tick checks.

A Lyme vaccine is being developed – and is currently in late-stage clinical trials – by Pfizer and Valneva. Approval by federal regulators will probably take about two more years, according to news reports.

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