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Respiratory Illness Data

This page is a summary of the latest information on viral respiratory illness in Wisconsin. It shows the respiratory illness activity level and trajectory for the previous week and provides key findings regarding respiratory virus transmission in Wisconsin. Some of this information, and more detailed information about influenza virus transmission, can be found in the Weekly Respiratory Surveillance Report, P-02346.

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The respiratory illness activity level includes illnesses associated with COVID-19, influenza, RSV (respiratory syncytial virus), and general respiratory illnesses, such as cough or sore throat. The activity level is a good measure for the overall trend of respiratory illness but does not reflect illness due to a specific virus or bacterium.

Even when respiratory illness levels are low, it is important to keep up with prevention strategies, such as staying up-to-date with vaccines, improving the air quality you breathe, practicing good hygiene, and staying home if you are sick. Additional precautions, such as wearing a mask and physical distancing, should be considered when illness levels are moderate or high or if you or people around you have risk factors for severe illness.

 Additional respiratory illness data

Click the buttons below to see the percent of emergency department (ED) visits for a respiratory illness or the percent of laboratory tests that are positive for respiratory viruses.

Key findings

  • Overall, respiratory illness levels are low across Wisconsin. Remember to keep up with core prevention strategies and consider using additional prevention strategies if you or the people around you have risk factors for severe illness.
  • COVID-19, influenza, and RSV are circulating at low levels.
  • Rhino/enterovirus, human metapneumovirus, and parainfluenza virus activities are elevated in Wisconsin.
  • Parainfluenza 3 is the predominant parainfluenza virus and is associated with bronchitis and bronchiolitis among children. 
  • DHS has dashboards displaying vaccination rates for COVID-19, influenza, and RSV.
  • For information about the current situation regarding highly pathogenic avian influenza (HPAI) A(H5N1), visit our Avian Influenza A Virus webpage.

Data shown are subject to change. Past data will be updated as more information is available.

How to use the data visualizations

The dashboard on this page provides the percent of all emergency department (ED) visits with a diagnosis of a respiratory illness by week. Users can hover over the trend link on the “respiratory illness trends” visualization to see more detailed information.

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 emergency departments (EDs) are represented in the dataset, and most EDs transmit visit information into ESSENCE within 24 hours.

ED visits for respiratory illness are ED visits meeting the CDC Broad Acute Respiratory Discharge Diagnoses (DD v1) ESSENCE category, which measures acute respiratory infection (ARI). This measure uses diagnoses for viral illnesses such as COVID-19, influenza, and RSV, in addition to general respiratory illnesses, such as cough or sore throat to measure the overall respiratory illness in the community.

Weekly proportion of ED visits for respiratory illness is calculated by dividing the number of visits to the ED with a diagnosis meeting the CDC Broad Acute Respiratory DDv1 definition from Sunday through Saturday by the total number of visits to the ED for the same time period.

Level metric: Activity level thresholds for the 2023-2024 respiratory season are calculated using the proportion of ED visits meeting the CDC Broad Acute Respiratory DDv1 definition from the 2018-19 respiratory season through the 2022-23 respiratory season. Data from the 2020-21 season and weeks 10-35 of the 2019-2020 season were excluded due to unusual transmission patterns during the COVID-19 pandemic. The highest 8 values from each season are used to create a distribution of values used to determine the thresholds limits. This is an adaptation of the moving epidemic method (MEM) used frequently in influenza surveillance.

Respiratory illness levelPercentilePercent of ED visits for ARI during 2023-2024 season
Low0 to <50th0% to <16.4%
Medium50th to <75th16.4% to <19.6%
Medium-High75th to <90th19.6% to <23.2%
High90th to <98th23.2% to <28.6%
Very High98th or above28.6% or above

Trajectory metric: The weekly respiratory illness trajectory is the measure of change in the proportion of ED visits meeting CDC Broad Acute Respiratory DDv1 definition from the previous week to the next week. To be considered growing or shrinking, the percent change of the proportion of ED visits meeting this definition from the previous week to the current week must be at least 5%, or the percent change must be consistently higher or lower each week compared with the previous three weeks and the percent change from three weeks previous to the current week must be at least 5%.

Additional resources

CDC Companion Guide: NSSP Emergency Department Data on Respiratory Illness.

Read more about the moving epidemic method: Rakocevic B, Grgurevic A, Trajkovic G, Mugosa B, Sipetic Grujicic S, Medenica S, Bojovic O, Lozano Alonso JE, Vega T. Influenza surveillance: determining the epidemic threshold for influenza by using the Moving Epidemic Method (MEM), Montenegro, 2010/11 to 2017/18 influenza seasons. Euro Surveill. 2019 Mar;24(12):1800042. doi: 10.2807/1560-7917.ES.2019.24.12.1800042. PMID: 30914080; PMCID: PMC6440585.

Last revised May 23, 2024