Ticks in Wisconsin: Data and Surveillance
This page showcases tick data in Wisconsin through tick surveillance reports and emergency department data due to tick bites. Tick exposure can occur year-round, but ticks are most active during warmer months (April-September). After you, your family members, or your pets spend time in the woods or areas with tall grass or brush, it is always important to check for ticks, especially in the spring, summer, and early fall. Learn more about ticks.
Wisconsin tick bite tracker
The Wisconsin Department of Health Services monitors emergency department (ED) data for people seeking medical care for tick bite-related concerns throughout Wisconsin. Looking at trends in tick bite-related ED visits helps people see when they are likely to be at higher risk for tick bites. The interactive tick bite tracker allows you to view statewide and regional trends in tick bite-related ED visits and compare data for the past five years. Ticks are most active in Wisconsin from spring through fall, but you should use caution throughout the year.
Additional tick bite data in Wisconsin
Data in the following accordions summarize tick activity in Wisconsin and allow you to compare the rate of tick bite-associated ED visits by public health region.
Compare the rate of tick bite-associated emergency department (ED) visits per 10,000 ED visits by public health region
Data shown are subject to change and may be updated as more information is available.
Past trends in ED visits for tick bites during the year have corresponded closely with what we know about the tick life cycle. For example, when tick bite-related ED visits begin to increase in the spring, it typically corresponds with our observance of adult ticks becoming more active in the environment. The spring increase then moves into the summer peak which corresponds with when we typically see the emergence of nymphal stage ticks.
How to use the data visualizations
The two visualizations on this page are interactive and provide the rate of tick-associated visits per 10,000 ED visits by week.
The first visual includes data for tick-associated ED visits for 2024 and 2025. You can add additional years’ data for 2021, 2022 or 2023 by clicking the check boxes. You can also use the dropdown menu to filter and view data for one of the five Wisconsin public health regions.
The second visual allows the user to examine patterns of disease activity across Wisconsin public health regions by week for the previous year.
Technical data notes and data sources
Data source: ESSENCE (Electronic Surveillance System for Early Notification of Community Based Epidemics) from the National Syndromic Surveillance Program.
Approximately 95% of non-federal Wisconsin EDs are represented in the dataset, and most EDs transmit visit information into ESSENCE within 24 hours.
Combinations of specific words and ICD diagnostic codes are typically used to identify emergency department visits by patients with specific concerns. However, there is not an ICD code for “tick bite,” so we were not able to use ICD codes to detect these visits. Instead, records containing the various spellings of the word “tick” or the combination of the “tick” and “bite” are located and counted.
Weekly rate of tick bite-associated ED visits are calculated by adding the number of visits to the ED with a diagnosis meeting the above definition during a week (Monday through Sunday) and then dividing that number by the total number of visits to the ED for the same week. This value is multiplied by 10,000 to express the value as a rate per 10,000 visits.
Tick surveillance report
The bi-weekly Tick Surveillance Report summarizes tick activity in Wisconsin based on tick collections from three sentinel sites in Iowa County, Lincoln County, and Waupaca County. The most recent report and all tick reports for the 2025–2026 tick season are available.
View the tick surveillance reports
Tick ID service
Have you recently found or removed a tick from yourself, your child, or your pet and want to learn more about it? The Wisconsin Department of Health Services offers a fast and simple Tick Identification Service based on a few questions and photographs you submit online. You can send a submission if you live in Iowa, Illinois, Michigan, Minnesota, and Wisconsin.
Important note: The Tick Identification Service cannot determine if the tick you found was carrying any germs or whether it made you sick. If you were bitten by a tick, or think you may have been bitten, monitor yourself for rash, fever, new muscle and joint pain, and new fatigue for 30 days. If any of these symptoms occur, contact your health care provider immediately. The only way to know if a tick made you sick is through an evaluation, and sometimes a blood test, performed by a health care provider. If you were bitten by a tick and live in Wisconsin where Lyme disease is common, consider contacting a health care provider right away to see if a single dose of antibiotics may be appropriate to help prevent Lyme disease.