Emergency Department Visit Data for COVID-19, Influenza, and RSV
This page provides the percent of all emergency department (ED) visits with a diagnosis of COVID-19, influenza, or RSV (respiratory syncytial virus) by week.
The activity levels of COVID-19, influenza, and RSV in the ED are shown below and whether COVID-19, influenza, and RSV are increasing, decreasing, or stable in the previous week. In addition, ED visit data for these viruses are shown by age group.
Additional respiratory illness data
Click the buttons below to see a current summary of respiratory virus activity or to see the percent of emergency department (ED) visits for a respiratory illness.
ED visits and activity levels for COVID-19, influenza, and RSV
ED visits for COVID-19, influenza, and RSV for different age groups
ED visits by age groups for COVID-19, influenza, and RSV
Data shown are subject to change. Past data will be updated as more information is available.
How to use the data visualizations
The three dashboards on this page are interactive and provide the percent of all emergency department (ED) visits with a diagnosis of COVID-19, influenza, or Respiratory Syncytial Virus (RSV) by week. Users can choose to view the data in these dashboards by using the hover options, changing the dates, or by clicking on dashboard buttons. Data are available since the week of September 7, 2019.
The first visual includes data for all age groups and includes activity levels and trajectory for each virus. The second visual allows the user to examine patterns of disease activity in a certain age group. For example, comparing the proportion of ED visits for COVID-19, RSV, and flu among those aged 0-4 years. The third visual allows the user to examine patterns of disease activity across age groups for the selected disease. For example, comparing the proportion of ED visits for COVID-19 among those aged 0-4 years with the proportion of ED visits for COVID-19 visits among those aged 65 years and older.
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.
The following ESSENCE diagnosis categories were used to define acute respiratory infection (ARI), COVID-19, influenza, and RSV:
- Acute Respiratory Illness (ARI): CDC Broad Acute Respiratory DDv1
- COVID-19: CDC COVID-Specific DDv1
- Influenza: CDC Influenza DD v1
- RSV: CDC Respiratory Syncytial Virus DDv1
Weekly percent of ED visits for ARI, COVID-19, influenza, and RSV are calculated by dividing the number of visits to the ED with a diagnosis meeting an above definition from Sunday through Saturday by the total number of visits to the ED for the same time period.
Level metric: Influenza and RSV activity level thresholds are calculated using the proportion of ED visits for influenza or RSV 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. COVID-19 activity level thresholds are calculated using the 2021-2022 and 2022-2023 seasons. For influenza and RSV, the highest 8 values from each season were used to create a distribution of values used to determine the thresholds limits; the highest 15 values were used for COVID-19. Metrics were calculated separately for each virus. This is an adaptation of the moving epidemic method (MEM) used frequently in influenza surveillance.
| Level | Percentile | Percent of weekly ED visits for COVID-19 | Percent of weekly ED visits for influenza | Percent of weekly ED visits for RSV |
|---|---|---|---|---|
| Low | 0 to <50th | 0% to <2.5% | 0% to <2.3% | 0% to <0.6% |
| Medium | 50th to <75th | 2.5% to <3.0% | 2.3% to <3.8% | 0.6% to <0.85% |
| Medium-High | 75th to <90th | 3.0% to <3.5% | 3.8% to <5.9% | 0.85% to <1.1% |
| High | 90th to <98th | 3.5% to <4.2% | 5.9% to <10.3% | 1.1% to <1.7% |
| Very High | 98th or above | 4.2% or above | 10.3% or above | 1.7% or above |
Trajectory metric: The weekly trajectory is the measure of change in percentage of ED visits diagnosed with COVID-19, influenza, or RSV from the previous week to the following week. To be considered growing or shrinking, the percent change of the proportion of ED visits for a diagnosis from the previous week to the current week must be at least 10%, 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 10%.
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.