Wisconsin is one of the highest-risk states in the country for tick-borne disease, and 2026 is shaping up as a particularly active tick year. The state recorded 18 Powassan virus cases in 2025 — the highest annual total ever — and experts at the University of Wisconsin are warning that mild winter temperatures have set the stage for a heavy 2026 season. Here is a complete guide to the ticks in Wisconsin, the diseases they carry, where risk is highest, and how to protect yourself and your family.
This article is for educational and informational purposes only. If you have been bitten by a tick or are experiencing symptoms of tick-borne illness, contact a healthcare professional immediately.
Tick Species in Wisconsin
Three tick species are the primary concern for Wisconsin residents and visitors:
| Tick Species | Common Name | Primary Diseases |
| Ixodes scapularis | Black-legged tick / Deer tick | Lyme disease, anaplasmosis, babesiosis, Powassan virus |
| Dermacentor variabilis | American dog tick / Wood tick | Rocky Mountain spotted fever, tularemia |
| Amblyomma americanum | Lone star tick | Ehrlichiosis, STARI; alpha-gal syndrome (red meat allergy); rising concern in WI |
The black-legged tick (deer tick) is by far the greatest disease concern in Wisconsin, as it is the primary vector for multiple serious illnesses including Lyme disease and the rapidly increasing Powassan virus. Bayfield County Health Department in northern Wisconsin specifically flags the lone star tick as a ‘rising concern’ in the region as of 2026, consistent with its northward expansion driven by climate change.
Deer Ticks in Wisconsin: Identification and Distribution
The black-legged tick — universally called the ‘deer tick’ in Wisconsin — is Ixodes scapularis. It is the smallest and most dangerous of Wisconsin’s common tick species:
- Adult females: Approximately 2-3mm long (slightly smaller than a sesame seed); reddish-orange body with a distinctive black shield (scutum) immediately behind the head; legs are black
- Adult males: Slightly smaller than females; uniformly dark brown to black
- Nymphs: Approximately 1-2mm (poppy seed size); tan or pale brown; six tiny legs — the stage most likely to bite humans and transmit disease because they are so small they are frequently missed
- Larvae: Approximately 1mm; six-legged; pale white or tan; even smaller than nymphs; rarely transmit disease because they have not yet fed on an infected host
Deer ticks are found throughout Wisconsin but are most common in the northern and central forested regions. They require moist, wooded habitats with leaf litter and are closely associated with white-tailed deer populations (deer are the primary host for adult deer ticks) and white-footed mice (which serve as reservoir hosts for the bacteria and viruses deer ticks carry). Wisconsin DHS monitors deer tick populations through a bi-weekly Tick Surveillance Report based on collections at three sentinel sites in Iowa County, Lincoln County, and Waupaca County.
Lyme Disease in Wisconsin
Lyme disease is the most common tick-borne disease in Wisconsin and in the United States overall. Wisconsin is one of 14 high-incidence Lyme disease states that together account for approximately 95% of all US cases. The disease is caused by the bacterium Borrelia burgdorferi, transmitted by the deer tick after attachment of approximately 24 to 48 hours.
The University of Wisconsin’s tick research program and the Wisconsin DHS have both flagged 2026 as potentially a ‘big year’ for Lyme disease in the state. WPR (Wisconsin Public Radio) reported in April 2026 that tick activity is already higher than the same period in 2025, and health professionals are preparing for increased case counts. Mild winter temperatures in many Wisconsin regions meant that adult deer ticks — which remain active whenever temperatures exceed 40°F — had extended activity periods in late 2025 and early 2026.
Lyme disease symptoms include:
- Early localized infection (days 3-30 after bite): Expanding rash at bite site (erythema migrans — the characteristic bull’s-eye rash, though not always present or recognizable); flu-like symptoms including fever, fatigue, headache, muscle and joint aches
- Early disseminated infection (days to weeks after bite): Multiple rashes, facial palsy, neck stiffness, heart palpitations, nerve pain
- Late disseminated infection (months after bite, if untreated): Arthritis (particularly large joints), neurological symptoms, cognitive problems
Early antibiotic treatment with doxycycline or amoxicillin is highly effective. Untreated or undertreated Lyme disease can become chronic and debilitating.
Powassan Virus in Wisconsin: A Growing Concern
Wisconsin’s Powassan virus situation is one of the most significant emerging tick-borne disease stories in the Upper Midwest. According to Wisconsin DHS data:
- The first Wisconsin Powassan case was identified in 2003
- As recently as 2017, Wisconsin had recorded the virus only a handful of times in its entire history
- 2025 saw 18 reported Powassan cases — the highest annual total ever recorded in the state
- 85 total probable and confirmed Powassan cases have been reported in Wisconsin from 2003 through 2025
- Cases are concentrated in the northern half of Wisconsin, where deer tick populations are denser
Bayfield County — in far northern Wisconsin — has been particularly affected. The county recorded 3 Powassan cases in 2024 and another 3 in 2025. The Bayfield County Health Department, in partnership with Marshfield Clinic Research Center, launched a tick collection and testing program in spring 2026 specifically to test adult and nymph ticks for Powassan virus in the region.
Patrick ‘PJ’ Liesch, the entomologist who directs the University of Wisconsin Insect Diagnostic Lab, warned in April 2026 that ‘reports thus far suggest that 2026 could be a heavy tick year’ due to mild winter temperatures allowing extended tick activity.
Unlike Lyme disease, which requires 24-48 hours of tick attachment for transmission, Powassan virus can transmit in as little as 15 minutes. There is no treatment and no vaccine.
Anaplasmosis in Wisconsin
Anaplasmosis (caused by Anaplasma phagocytophilum) is a significant and underreported tick-borne disease in Wisconsin transmitted by the deer tick. Symptoms typically appear 1 to 2 weeks after a tick bite and include fever, severe headache, chills, muscle aches, and fatigue. Some patients also develop nausea, vomiting, or decreased appetite. Without treatment, anaplasmosis can progress to severe illness including respiratory failure and neurological complications. Doxycycline is the recommended treatment and is highly effective when started promptly. Anaplasmosis is reportable in Wisconsin and Wisconsin DHS tracks annual cases.
Babesiosis in Wisconsin
Babesiosis is a parasitic infection of red blood cells caused by Babesia microti and transmitted by the deer tick. It causes fever, chills, sweats, headache, fatigue, and hemolytic anemia. Most healthy adults experience mild illness, but it can be life-threatening in people who are elderly, immunocompromised, or asplenic (without a spleen). Babesiosis is treated with a combination of antiparasitic drugs plus doxycycline. In Wisconsin, babesiosis is more commonly reported in the northern regions of the state where deer tick density is higher.
Ehrlichiosis in Wisconsin
Ehrlichiosis in Wisconsin is transmitted primarily by the lone star tick (Amblyomma americanum), which is spreading northward into the state. Symptoms include fever, headache, chills, muscle aches, and occasionally rash. It is treated effectively with doxycycline. As the lone star tick expands its range in Wisconsin and Minnesota, ehrlichiosis is expected to become increasingly common in the Upper Midwest.
Alpha-Gal Syndrome: The Lone Star Tick’s Other Impact
The lone star tick can trigger alpha-gal syndrome (AGS) — an allergy to alpha-galactose, a sugar molecule found in red meat (beef, pork, lamb) and other mammalian products. A bite from the lone star tick sensitizes some people to alpha-gal, causing allergic reactions ranging from hives and gastrointestinal symptoms to anaphylaxis when eating red meat, sometimes hours after consumption.
Alpha-gal syndrome is an emerging concern in northern Wisconsin and Minnesota as the lone star tick’s range expands. The CDC began tracking alpha-gal syndrome more systematically in 2023. Bayfield County Health Department specifically flags the lone star tick as a ‘rising concern’ for northern Wisconsin in 2026, citing its presence in the region.
New Tick-Borne Diseases in Wisconsin and Minnesota
The ‘new tick disease in Wisconsin’ and ‘new tick disease Minnesota’ searches reflect growing awareness of two developments:
1. Powassan Virus as a ‘New’ Significant Threat
While Powassan was first identified in 1958, its rapid emergence in Wisconsin — from a handful of historical cases to 18 in 2025 alone — effectively makes it a new significant tick-borne threat for Wisconsin residents. The expansion of deer tick populations and the growing prevalence of Powassan’s deer tick virus (lineage II) in the deer tick population are driving this increase. For Wisconsin residents who were not previously concerned about Powassan, the 2024-2025 case surge represents a new reality.
2. Lone Star Tick Expansion Bringing New Diseases
The northward expansion of the lone star tick into Wisconsin and Minnesota represents a genuine emergence of previously uncommon diseases in the region. Ehrlichiosis and alpha-gal syndrome, historically uncommon in the Upper Midwest, are increasing as the lone star tick establishes populations in these states. Bayfield County specifically cites the lone star tick as ‘of rising concern’ in northern Wisconsin, and the tick’s continued northward range expansion driven by warming temperatures means this trend is expected to continue.
Where Are Ticks Most Common in Wisconsin?
Wisconsin’s tick distribution is not uniform across the state:
- Northern Wisconsin (Bayfield, Ashland, Iron, Vilas, Oneida, Lincoln counties and surrounding areas): Highest deer tick density; highest Powassan and Lyme disease risk; heavily forested with significant white-tailed deer populations; most Powassan cases occur here
- Central Wisconsin (Marathon, Waupaca, Portage, Wood counties): Significant deer tick presence; actively monitored by Wisconsin DHS Tick Surveillance program at Waupaca County sentinel site
- Southern and western Wisconsin (Iowa County and surrounding): Also monitored by Wisconsin DHS; deer tick present but generally lower density than the north
- Statewide: American dog ticks (wood ticks) are found throughout Wisconsin, particularly in unmowed grassy areas, farm fields, and woodland edges — common in all regions
When Are Ticks Active in Wisconsin?
Tick activity in Wisconsin follows a seasonal pattern tied to temperature and tick life stage:
- March–May: Adult deer ticks resume activity as temperatures rise above 40°F; these are the overwintered adults that are the first significant risk of the new season. American dog ticks begin emerging
- May–July: Nymph deer ticks — the smallest and hardest to detect stage, and the stage most responsible for disease transmission — become highly active. This is the peak risk period for Lyme disease and Powassan transmission
- August–September: Nymph activity declines; new generation of adult deer ticks begins to emerge
- October–November: Adult deer tick activity peaks again in fall. American dog tick activity declines
- Winter: Adult deer ticks remain active on mild days whenever temperatures exceed 40°F; do not assume the risk is gone because it is cold — check after outdoor activity in winter if temperatures have been above freezing
Wisconsin Tick Identification Service
Wisconsin DHS offers a free online Tick Identification Service for residents of Wisconsin, Minnesota, Iowa, Illinois, and Michigan. If you find a tick on yourself, a family member, or a pet, you can submit a few questions and photographs through the Wisconsin DHS website (dhs.wisconsin.gov/tick) to receive species identification.
Important note: This service identifies the species of tick but cannot determine whether the tick was carrying any disease-causing organisms or whether it made you sick. For any health concerns after a tick bite, consult a healthcare provider. Monitor yourself for rash, fever, new muscle and joint pain, and new fatigue for 30 days after any tick bite.
Tick Prevention in Wisconsin
The same prevention strategies that work in Massachusetts and other high-tick states apply in Wisconsin:
Repellents
- DEET (20% or higher) applied to exposed skin — effective against deer ticks, dog ticks, and lone star ticks
- Picaridin — equally effective to DEET, less greasy feel, safe for use on children
- IR3535 and oil of lemon eucalyptus — alternatives for those avoiding DEET
- Apply to lower half of the body especially — Wisconsin tick researchers recommend concentrating repellent on areas where ticks are most likely to climb (legs, ankles, waist)
Permethrin-Treated Clothing
- Permethrin applied to clothing kills ticks on contact; can be purchased pre-treated or applied at home
- Particularly effective for high-exposure activities like hunting, hiking, trail work, and gardening in Wisconsin’s wooded areas
Clothing and Habits
- Tuck pants into socks when walking in wooded or grassy areas
- Wear light-colored clothing — makes ticks visible before they reach the skin
- Shower within 2 hours of outdoor activity to wash off unattached ticks
- Perform a full body tick check daily after outdoor activity; focus on scalp, behind ears, armpits, belly button, groin, and behind knees
Pet Protection
- Use veterinarian-recommended tick prevention products on dogs year-round in Wisconsin
- Dogs are major tick carriers into the home; protecting your dog also protects your family
Frequently Asked Questions
What tick diseases are in Wisconsin?
Wisconsin residents face risk from Lyme disease (most common), anaplasmosis, babesiosis, Powassan virus (increasing rapidly — 18 cases in 2025), Rocky Mountain spotted fever, ehrlichiosis (increasing with lone star tick expansion), and alpha-gal syndrome. Wisconsin is one of the highest-risk states in the US for tick-borne disease.
Are there deer ticks in Wisconsin?
Yes — the black-legged tick (Ixodes scapularis), commonly called the deer tick, is found throughout Wisconsin and is most common in the northern and central forested regions. Deer ticks are the primary vector for Lyme disease, anaplasmosis, babesiosis, and Powassan virus in Wisconsin.
What is the new tick disease in Wisconsin?
Two developments drive searches for ‘new tick disease Wisconsin’: (1) Powassan virus, which surged to a record 18 cases in Wisconsin in 2025 after being historically rare in the state — this is the most significant new tick-borne disease concern in Wisconsin; and (2) the northward expansion of the lone star tick, which brings ehrlichiosis and alpha-gal syndrome (red meat allergy) into areas where these were previously uncommon.
How many Powassan cases has Wisconsin had?
Wisconsin recorded 85 total probable and confirmed Powassan cases from 2003 through 2025. In 2025 alone, 18 cases were reported — the highest annual total ever recorded in the state. Bayfield County in northern Wisconsin recorded 3 cases in 2024 and 3 more in 2025, confirming back-to-back years of elevated local activity.
What tick diseases are in Minnesota?
Minnesota’s tick-borne disease profile is nearly identical to Wisconsin’s, as both states share the same tick species distribution and geographic characteristics. Lyme disease, anaplasmosis, babesiosis, Powassan virus, ehrlichiosis, and the expanding lone star tick are all relevant concerns in Minnesota. Wisconsin DHS’s Tick Identification Service covers Minnesota residents as well.
Final Thoughts
Wisconsin’s tick-borne disease situation in 2026 is more serious than it has been historically, driven primarily by two developments: the dramatic rise in Powassan virus cases (from a handful of historical cases to 18 in 2025 alone) and the continued northward expansion of the lone star tick bringing new diseases into the Upper Midwest. For Wisconsin residents — particularly those in northern counties and anyone spending time in wooded or brushy areas — tick prevention is a year-round health priority, not just a summer concern. The Wisconsin DHS offers active surveillance data, a tick identification service, and updated guidance through its tick-borne disease portal, which is the best source for current case counts and local risk information as the 2026 season develops.
This article is for educational and informational purposes only. Consult a healthcare professional for any medical concerns related to tick bites or tick-borne illness.