Lyme disease cases plummeted in Maine in 2020 with the decline likely driven by dry weather last summer and the reluctance of people to seek medical care during the early stages of the COVID-19 pandemic.

Lyme cases declined nearly 50 percent in Maine last year, from 2,167 cases in 2019 – a record high – to 1,115 in 2020, according to the Maine Center for Disease Control and Prevention.

But Griffin Dill, integrated pest management professional at the University of Maine Cooperative Extension’s “tick lab,” said deer ticks – the arachnids that transmit Lyme disease – are already emerging with the warmer weather and it seems unlikely that reduced Lyme cases in 2020 means that tick populations are down. Dill said it’s early in the spring, but so far tick activity seems normal.

Anaplasmosis and babesiosis cases – also caused by the deer tick – also were down in 2020. Anaplasmosis declined 43 percent, from 685 cases in 2019 to 389 in 2020, while babesiosis cases decreased 52 percent, from 138 in 2019 to 66 in 2020.

Dill said a drier than normal June and July led to nymph ticks, the tiny adolescent ticks that are much harder for people to spot than adult ticks, becoming less active, and less likely to be questing for a host.

“During the active surveillance that we do of ticks, we were struggling to find the nymph ticks last summer,” Dill said. But Dill said adult populations seemed normal in the fall.


Megan Porter, vector-borne disease public health educator, said the low numbers from 2020 are likely “multifactorial” but that weather did play a role.

“The ticks don’t tolerate dry weather very well. When we got the abnormally dry weather last summer, the ticks hunker down in the leaf litter and wait for better days,” Porter said.

Porter said another potential factor is that the COVID-19 pandemic may have changed how people were interpreting their symptoms, and they may have been less likely to consider Lyme disease or get tested for the bacterial infection. Some of the symptoms of Lyme disease, such as fever, headache and fatigue, may have been misinterpreted as COVID-19 symptoms. People may have sought out COVID-19 tests, and when they tested negative for COVID-19, did not consider that they may have contracted Lyme disease, Porter said.

Dill said another possibility is that people may have been reluctant to access the health care system last year and ignored the Lyme symptoms as the pandemic worsened and some health services were curtailed.

“There may have been a lot of untreated Lyme disease last year,” Dill said.

He said it wasn’t because people were being less active outdoors. In fact, the opposite was likely true. With much of society shut down last spring, people were spending more time hiking and pursuing outdoor activities. Dill said a survey the tick lab conducted last year of about 3,000 people showed that 36 percent said they had increased their outdoor activities in 2020.

To prevent tick bites, when out in tick habitat – such as hiking in the woods or moving firewood – use bug repellant, wear light-colored, long clothing and search for ticks after you get home.

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