A Boise lawsuit alleged Lyme disease was contracted in Idaho. Is that likely?

The recent settlement of a lawsuit between a Boise teacher and the school district over an alleged mouse infestation in a classroom raised an unusual question:

Can you contract Lyme disease in Idaho?

The general scientific consensus seems to be no, while Michelle Chung’s lawsuit asserted otherwise.

Among other things in her filing, Chung accused the Boise School District of violating the Family Medical Leave Act when she was out because of a diagnosis of two tick-borne diseases. “In July 2024, Chung was diagnosed with Babesiosis and Anaplasmosis, both coinfection of Lyme,” according to the lawsuit, which alleged that those infections were the result of “persistent mice exposure at West Junior High.”

Although the lawsuit was settled, the school district denied any admission of liability.

The ticks responsible for transmitting these diseases — which go to animals, such as mice, to humans — aren’t thought to live in Idaho. So what do Boise residents need to know about the risks of Lyme disease in the area?

The Idaho Statesman spoke with Dana Shaw, an associate professor at Washington State University who specializes in tick-transmitted diseases, to learn more about how Lyme is spread and whether it’s likely to be contracted in Idaho.

The ticks are the key

Lyme disease, babesiosis and anaplasmosis are all bacterial infections that are spread from small animals, such as birds and mice, to humans by two species of ticks: blacklegged ticks and western blacklegged ticks. “You can have a single infection or a coinfection, and it is possible to be infected with all three of those things at the same time,” Shaw said.

Shaw clarified that each of these diseases is “a blood-borne infection, so it has to be transmitted through the bite of a tick.” That means that even though mice all around the country can carry these bacteria in their blood, humans are only at risk when blacklegged or western blacklegged ticks are around to bite the infected animal.

The U.S. Centers for Disease Control and Prevention carries out an extensive tick surveillance program every two years. Data from 2025 shows that blacklegged ticks live throughout the eastern half of the U.S., particularly in the Northeast. Western blacklegged ticks live primarily along the Pacific Coast but also have smaller populations in Utah, Arizona and potentially Nevada.

There are no known established populations of blacklegged or western blacklegged ticks in Idaho. According to Shaw, these ticks are picky about where they populate. They have certain requirements for humidity levels and don’t like hard freezes, and “they need it to be warm enough for a period of time so they can find a host.”

Shaw said changes in climate could cause these tick populations to spread, adding that “there’s longer, warmer active periods, you’ll see that they’re pushing into Canada now, too.”

There’s no evidence that those tick populations have spread into Idaho, but residents can keep an eye out and participate in the crowdsourced tick surveillance program TickSpotters. Submit a photo of the top side of a tick and experts will help identify it. That way, if blacklegged ticks make their way into the Gem State, Idahoans can help raise the alarm.

Simply finding one of the ticks doesn’t mean they’ve laid down roots in Idaho. Shaw said “ticks can come into areas by, say, falling off of birds or other large mammals.” A tick population is “established” when six or more are reported within a year, or if multiple life stages have been reported, according to the CDC.

Delayed diagnosis makes reporting cases tricky

According to the most recent data from the Idaho Department of Health and Welfare, there were 11 cases of Lyme disease reported in Idaho in 2023. “However, cases are reported by where people live and not where they were exposed. Most cases in Idaho had an out-of-state exposure,” IDHW spokesperson AJ McWhorter told the Statesman.

If you’ve ever heard of the “bull’s-eye” rash, called erythema migrans, associated with a Lyme-infected tick bite, you might be wondering how someone could travel out of the state and back without knowing they contracted Lyme. But according to the CDC, 20-30% of people never develop this rash, so diagnosis might have to rely on other symptoms.

Shaw explained that “the symptoms associated with Lyme disease tend to be kind of ambiguous and overlap with other things, like if you have a head cold, or you’re just not feeling very well, or if you’re having severe allergies.” Because of this, Lyme disease actually “can sometimes take years to diagnose,” she said.

Idaho residents may report sporadic cases of Lyme disease, but due to delays in diagnosis and the absence of blacklegged ticks, it is highly likely that the infection has occurred outside of Idaho.

Ticks you should look out for in Idaho

On your next stroll through the woods of Idaho, you probably don’t need to worry about Lyme disease, but still keep an eye out for ticks. Idaho is home to the Rocky Mountain wood tick and the brown dog tick, according to CDC surveillance maps, which can transmit serious diseases such as Rocky Mountain spotted fever, Colorado tick fever and tularemia.

In the event you get a tick bite, the CDC advises you to remove the tick carefully with tweezers and then wash the bite area as well as your hands. Before you get rid of the tick, consider snapping a photo of it and uploading it to TickSpotters to monitor existing tick populations and keep an eye out for new species.