Five years ago, finding a blacklegged tick in most of southern Michigan was uncommon enough to surprise a county health worker. That is no longer the case. The Michigan Department of Health and Human Services reported 1,215 Lyme disease cases in 2024, up from 452 in 2020, a 168% increase driven by the rapid geographic spread of Ixodes scapularis, the blacklegged tick responsible for transmitting the disease.
The MDHHS spring 2025 advisory warned that blacklegged ticks are now established in more Michigan counties than at any point on record. The agency’s public data highlights the 2020-to-2024 arc, and the overall trajectory, a 168% rise over five years with the steepest gains in the most recent years, underscores a dramatic acceleration in both tick spread and case detection across the state.
Where the ticks are showing up
Blacklegged ticks were once concentrated in western Michigan’s lakeshore counties and parts of the Upper Peninsula. Field surveillance now finds established populations across much of the Lower Peninsula, including counties in the southeast and central regions that had little recorded tick activity a decade ago.
In Kalamazoo County, health officials collected 24 blacklegged ticks during 2024 surveillance sweeps. Of those, seven tested positive for Borrelia burgdorferi, the bacterium that causes Lyme disease, and one carried Anaplasma phagocytophilum, the pathogen behind anaplasmosis. A nearly 30% Lyme positivity rate in a single county sample is not generalizable statewide, but it illustrates the kind of local risk that was virtually absent from that part of the state a few years ago.
“We used to go entire seasons without pulling a single blacklegged tick from our drag cloths in Kalamazoo County,” said a Kalamazoo County Health and Community Services spokesperson in the department’s 2025 public notice. “Now they are the most common species we collect, and a significant share are carrying Lyme-causing bacteria.”
The state’s MiTracking tick portal, which accepts specimens from residents and local partners, shows blacklegged ticks now dominating submissions. Federal tracking by the U.S. Centers for Disease Control and Prevention, which classifies county-level tick populations as either established or expanding, reflects the same pattern across the Great Lakes region.
Why the numbers need careful reading
Part of the increase is real biology: ticks spreading into new territory, aided by warmer seasonal temperatures, shifting land use, and robust deer populations that serve as key hosts. But part of it is better bookkeeping.
In 2022, the CDC implemented a revised national case definition for Lyme disease surveillance. The updated criteria broadened what qualifies as a reportable case, capturing more probable infections alongside laboratory-confirmed ones and standardizing reporting across states. A CDC analysis published in its Morbidity and Mortality Weekly Report explicitly cautioned that post-2022 case counts can reflect the methodological shift as much as actual disease spread.
Michigan has not published a formal breakdown separating the effect of the new definition from genuine increases in transmission. That means the 168% five-year rise should be read as a composite signal: more ticks carrying disease into more counties, and a surveillance system that is now catching infections it previously missed. Both forces are real. Their exact proportions remain unquantified at the state level.
Other gaps persist. MDHHS has not released demographic breakdowns of Michigan Lyme patients by age, sex, or occupation, nor has it published county-by-county trend data granular enough to show which areas face the fastest-growing risk. No peer-reviewed study specific to Michigan’s Lyme trajectory or tick-expansion modeling has appeared in the literature reviewed as of May 2025.
How Michigan compares
Michigan is not an outlier. Across the upper Midwest and Northeast, states have reported rising Lyme counts over the past decade as blacklegged tick populations push into higher latitudes. Wisconsin, Minnesota, and Pennsylvania have all documented similar expansions. What distinguishes Michigan’s recent data is the speed of the increase and the fact that large portions of the state went from minimal tick activity to established populations within a few years, compressing a transition that took longer in traditional Lyme hotspots like New England.
Michigan-specific protection for tick season
For Michigan residents heading into woods, fields, or even overgrown backyards between now and late fall, public health officials stress a layered defense tailored to the state’s landscape and tick behavior patterns.
Before you go out: Wear long sleeves and pants, tuck pants into socks, and choose light-colored clothing so crawling ticks are easier to spot. Treat clothing and gear with permethrin-based products designed for fabrics, and apply an EPA-registered repellent to exposed skin according to label directions. Michigan’s blacklegged ticks are most active from April through July and again in October and November, so vigilance should extend well beyond the summer months.
While outdoors: Stay on cleared trails when possible and avoid brushing against tall grass, leaf litter, and low shrubs where ticks wait with outstretched legs for a passing host. In Michigan, this includes the edges of wooded lots in suburban neighborhoods, not just remote forests. Residents in counties that historically saw few ticks, particularly in the southeast and central Lower Peninsula, should not assume their yards are tick-free.
After coming inside: Shower within two hours. Run hands over the scalp, behind the ears, under the arms, along the waistline, and behind the knees. Check children and pets the same way. Toss outdoor clothing into a hot dryer for at least 10 minutes to kill any ticks that hitched a ride.
If you find an attached tick: Use fine-tipped tweezers to grasp it as close to the skin as possible and pull straight up with steady pressure. Clean the bite with soap and water or rubbing alcohol. Saving the tick in a sealed bag can help a clinician later, and Michigan residents can also submit specimens through the state’s MiTracking tick portal to contribute to ongoing surveillance, though testing the tick itself does not replace a medical evaluation.
When to seek medical attention after a tick bite
A spreading rash, especially one with a bull’s-eye pattern, flu-like symptoms, joint pain, or unexplained fever following a tick bite or outdoor exposure should prompt a call to a health care provider. Early treatment with antibiotics is highly effective; delayed diagnosis is where Lyme disease causes the most lasting harm.
MDHHS has urged clinicians statewide to keep tick-borne illness on their radar when evaluating summer and early fall complaints, even in counties that historically reported few cases. “Providers should consider Lyme disease and other tick-borne infections in patients presenting with compatible symptoms, regardless of travel history, given the expanded range of blacklegged ticks in Michigan,” the agency stated in its May 2025 advisory. With blacklegged ticks now present across a wider swath of Michigan than ever documented, the old assumption that Lyme is someone else’s problem no longer holds.
More from Morning Overview
*This article was researched with the help of AI, with human editors creating the final content.
