COVID-19 Pandemic Vulnerability Index (PVI)
A collaborative effort developed this COVID-19 Pandemic Vulnerability Index (PVI) Dashboard. Scientists from NIEHS, North Carolina State University and Texas A&M University contributed to the effort.
Population-level data is a powerful resource for understanding how the virus is spreading and which communities are at risk. However, interpreting that information is challenging. The data visualization in this dashboard offers an effective means of communicating data to scientists, policy makers, and the public.
This dashboard creates risk profiles, called PVI scorecards, for every county in the United States. It is continuously updated with the latest data. The PVI summarizes and visualizes overall risk in a special version of a pie chart, called a radar chart, where different data sources make up pieces of the pie.
Instructions below tell you how to navigate the COVID-19 PVI Dashboard.
In Figure 1, within the map of the U.S., you see blue shading that corresponds to the overall PVI for each county. There are many options within the Dashboard to further explore the underlying sources of vulnerability. You’ll see that the Rank option is on by default, but can be toggled on and off. There are additional options to see more information. The “Slices” option shows special pie charts, known as a radar charts, which visually summarize a county's overall vulnerability to COVID-19.
Each slice of these radar charts, or PVI profiles, represents a different data source, described below. The information is combined to generate a PVI score for each county. This chart simultaneously shows the magnitude and source(s) of vulnerability.
There are also options to show cumulative case and death counts across the country.
Use the box in the lower right corner and mouse pointer to zoom on any part of the U.S. County and border lines will appear. Clicking on a county or PVI profile will cause a county scorecard to appear within the map pane.
You can click on and get data about any county, whether or not a PVI profile already appears. Default display settings show only radar charts for the top 250 counties by overall PVI score. You can adjust the number of charts displayed or specify counties to display in the Quick Filter box in the upper left corner.
Using the county of St. Francis, Arkansas, as an example, this section explains PVI Scorecards, which appear on the left side of the screen.
On the left side of Figure 2 is a PVI score distribution. Counties with the lowest vulnerability to COVID-19 appear on the left, while counties with highest vulnerability are on the right. Black vertical lines show where Adams County and St. Francis county are located within the distribution. Radar plots are shown above with information across the 12 slices comprising their PVI score.
On the right side of Figure 2, the PVI Scorecard for St. Francis shows data sources and their corresponding colors. Infection rates, depicted in red slices, are labeled 1 and 2. Intervention rates, noted in blue slices 5 and 6, are highly variable and are updated daily. Population concentration and density are fixed values describing general demographic information, and these are shown in green slices 3 and 4. Health and Environmental variables are shown in the purple slices 7-12.
As shown in Figure 3, the fill within the slice indicates risk level within that metric category. Indication of the highest relative vulnerability (score = 1) is a slice filled all the way to the outer ring of the profile.
Slice coloring is used to indicate categories of different data streams. Details of the data sources are described on the Details page. The overall quantification and size of the PVI represents an overall vulnerability scorecard. Note that the PVI value is based on ranks, such that these values are relative and not tied to a unit. Also note that for all slices, a larger value represents higher vulnerability. For interventions, a larger slice represents low adherence and adoption of interventions.
Navigating the Dashboard
The advanced menu options in the upper-left corner,, allow you to search the map and customize the display.
Additionally, you can change the map itself through the Change Map Menu option. The default dark gray map can be changed to one of several options, including satellite images, topology maps, etc.
Within Legend, you can adjust the size and opacity of the graphic displayed on the map.
With the Filters options, you can create complex queries, or subsets, of information, and you can:
- Limit the number of scorecards displayed
- Change how those are ordered
- Specify counties to display by name
- Specify clusters of similar PVI profiles
- Restrict ranges for a slice or overall scores.
The default order is listed by the overall PVI, but it can also be ranked based on a data slice.
In the Specify Names box, you can list specific counties of interest using one per line while the Specify Clusters option will provide check boxes to show PVI profiles that look like one another or form a cluster of counties.
Many Filters options work together, so be aware of selections made across options.
Counties can be grouped together, or clustered, based on PVI similarity. Cluster membership is noted on the Scorecard for each county. Two types of clustering are available: hierarchical, or HClust, and KMeans.
Hierarchical clustering, as the name suggests, is an algorithm that builds hierarchy of clusters. This algorithm starts with all the data points assigned to a cluster of their own. Then, the two nearest clusters are merged into the same cluster. This algorithm terminates when there is only a single cluster left. Alternatively, KMeans clustering begins with a set number of clusters and finds the optimal grouping of counties into each of these clusters.
By clicking on the cluster numbers, the map will display only the counties within that cluster. It allows you to view counties with similar vulnerability profiles.
The Setting Summary option allows the user to save and/or retrieve settings from previous Dashboard navigation, to automate the re-evaluation of previous visualizations and filtering.
Toggle options allow you to remove the three panels shown from the display to maximize the map for higher resolution viewing.
Details of the current PVI, including model documentation, data sources, and performance evaluation, are available on the Details page.
Source Data links to the GitHub repository of all daily PVI data files.
Clicking on any county in the map will populate the county display box (lower left corner) and county-specific info panels along the bottom of the page. Within the display box, the 3-day average number of new Cases and Deaths and number of declining days (Days in the past two weeks where the number of new cases/deaths has declined or remain unchanged relative to the day before) are given. Clicking the magnifier icon will center and zoom to the map to the selected county.
The cumulative data date displayed for observed 'Cases' and 'Deaths' can be scrolled back to March 15, 2020. More options for adjusting this display layer are available under the 'Covid-19 Legend' menu option.
The observed number of Cases and Deaths for the selected county is shown for the preceding 14 days.
The predicted number of Cases and Deaths for a 14-day forecast horizon is plotted as a line within a shaded confidence interval.
A preprint describing the Dashboard and the underlying methods is available at medrxiv.org.
NIEHS: John House, Matthew Wheeler, and Alison Motsinger-Reif
NC State University: Skylar Marvel, Fred Wright, Yihui Zhou, and Kuncheng Song and David Reif
Texas A&M University: Weihsueh Chiu and Ivan Rusyn
Are You Ready to Get Started?Visit the COVID-19 Pandemic Vulnerability Index (PVI) Dashboard
Contact Alison A. Motsinger-Reif, Ph.D., chief of the NIEHS Biostatistics and Computational Biology Branch, with questions about this application.