Outpatient Influenza-Like Illness Data

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

How to use the data visualizations

The dashboards on this page are interactive and show summary data related to the proportion of outpatient and urgent care visits at participating health clinics for respiratory illnesses referred to as influenza-like illnesses. ILI is categorized into levels of low, moderate and high to describe the amount of influenza-like illness measured. These data are collected as part of Wisconsin’s participation in the CDC (Centers for Disease Prevention and Control) ILINet.

Users can interact with the data in these visualizations by using the hover options, changing the dates, or by clicking on buttons. Visualizations include a dropdown menu that allows the user to show a date for one of the five Wisconsin public health regions.

The influenza-like illness activity map and regional trends visual contains a map of influenza-like illness levels categorized as high, moderate, or low for a selected week for the entire state and by public health region. It also contains a graph displaying the proportion of visits for influenza-like illness by week with the color of the line indicating the influenza-like illness level of high, moderate or low. The week of the respiratory season displayed on the map can be adjusted by using the dropdown selection.

The influenza-like illness activity by influenza season visual shows the proportion of visits for influenza-like illness by respiratory season week stratified by respiratory virus season so that the intensities of different respiratory seasons can be compared.

Technical data notes and data sources

Data source: The data in these visualizations are reported from Wisconsin outpatient clinics and urgent cares who participate in the US Outpatient ILINet.

Providers who participate in ILINet report weekly to the CDC and Wisconsin Department of Health Services (DHS) on the number of patient visits that week to their clinic and the number of visits that meet a case definition for an ILI. ILI is defined as fever (temperature of 100˚F or higher) and a cough and/or a sore throat.

ILI categories

ILINet categories of high, moderate and low were calculated by comparing the percent of outpatient visits due to ILI that week to the average percent of ILI visits that occur during weeks with little or no influenza virus circulation during the past several respiratory virus seasons. Levels are calculated each season using the three previous seasons’ data.

Each year, weeks from the previous three respiratory virus seasons when the number of influenza positives reported by the Wisconsin State Laboratory of Hygiene made up less than 2% of the total season’s influenza positive specimens were defined as “non-influenza weeks.” Thresholds were calculated using these “non-influenza weeks.” The mean proportion of visits for ILI were calculated during these weeks, the “baseline” value was defined as the mean proportion of visits for ILI plus two standard deviations, the “threshold” value was defined as the mean proportion plus four standard deviations. This was done for statewide and regional data.

Low levels of ILI were defined in the displayed seasons as proportions of visits for ILI that fell below the baseline values, moderate levels were those that fell between the baseline and threshold values, and high levels were those that fell above the threshold values.

Baseline and threshold values for each season is displayed as follows: