COVID-19, Influenza, and RSV-Associated Hospitalizations
Hospitalization rates of respiratory viruses can provide information on illness burden and severity. This page provides the rate and number of hospitalizations that occurred due to COVID-19, influenza, or respiratory syncytial virus (RSV) infection and were reported to the Wisconsin Electronic Disease Surveillance System (WEDSS). Data are available by Wisconsin public health region and by age group.
Additional respiratory illness data
Click the following buttons to see a current snapshot summary of respiratory virus activity, the percent of emergency department (ED) visits for a respiratory illness, the laboratory testing data for respiratory illnesses, or respiratory virus death data.
Data shown are subject to change and will be updated as more information is available.
How to use the data visualization
The dashboards on this page are interactive and show rates or counts of hospitalizations due to COVID-19, influenza, and RSV infections. Users can interact with the data in these visualizations by using the hover options, changing the dates, or by clicking on buttons.
The first visual shows age-adjusted hospitalization rates per 100,000 people for COVID-19, influenza, and RSV. Rates are age-adjusted to the population of Wisconsin during 2022. Age adjustment, or age standardization, is used in epidemiology to allow populations to be compared directly when the age distribution of whom most commonly gets seriously ill from the disease is skewed. Risk of hospitalization varies by age for respiratory viruses, such as COVID-19, influenza, and RSV, and different regions of Wisconsin have different age distributions. For this reason, we used age adjustment so that rates of hospitalization could be compared for different regions of Wisconsin. The dashboard includes a dropdown menu allowing you to filter and show data for one of the five Wisconsin public health regions. The “Show number of cases” button allows the user to see the number of hospitalizations for each virus rather than the rates. The date slider allows you to adjust the date range displayed. Data are available since the week of November 1, 2023.
The second visual displays rates of reported hospitalizations for COVID-19, influenza, or RSV by four age groups. The user has the option to select which virus’s data they would like the visualization to display. The visualization displays approximately one year, or 52 weeks, of data.
The third visual displays rates of reported hospitalizations for COVID-19, influenza, or RSV for one age group at a time. The user has the option to select which age group’s data they would like the visualization to display. The visualization displays approximately one year, or 52 weeks, of data.
The fourth visual displays the number of reported hospitalizations for COVID-19, influenza, or RSV by four age groups. Similar to the second visualization, the user has the option to select which virus’s data they would like to view. On the left side of this visualization, the horizontal bars show the proportion of all hospitalizations by age group for the selected virus during the approximately one year, or 52 weeks, of data that is displayed.
Technical data notes and data sources
Data source: WEDSS. COVID-19- and RSV-associated hospitalization have been reportable in Wisconsin since November 1, 2023. Influenza-associated hospitalizations have been reportable electronically since the 2010 season.
COVID-19-, influenza-, and RSV-associated hospitalizations are reportable conditions, and must be reported within 72 hours of recognition. Hospitalizations for these viruses are defined as inpatient hospitalizations resulting from clinically compatible illnesses that were diagnosed by appropriate laboratory tests—generally, polymerase chain reaction (PCR) tests.
Crude hospitalization rates were calculated by dividing the number of hospitalizations for each virus each week by the population of Wisconsin, or the population of the region or age group in question. These rates were multiplied by 100,000 to represent the crude hospitalization rate per 100,000 population.
Age-adjusted hospitalization rates were determined by:
- Calculating the crude age-specific rates (not age adjusted) for each Wisconsin region by dividing the number of people with a COVID-19-, influenza-, or RSV-associated hospitalization in each age group in a specific region by the total population in that age group in that region.
- Calculating the age-group weights in the standard population (by dividing the number of people in each age group by the total population). Our standard population was the 2022 Wisconsin population.
- Multiplying the age-specific crude rate by the age-group weight and summing these values in each region to calculate the age adjusted rate for that region.
- Multiplying the age-adjusted rate by 100,000 to represent the rate per 100,000 population.