The map displayed in a COVID data browser is analogous to a weather map, showing the intensity and location of "storms" of COVID activity.

Cumulative case count

This is the total confirmed case count by county for the currently selected "pertainsDate".

Cumulative death count

This is the total death count of patients with confirmed cases for the currently selected "pertainsDate". Again the data is by county.

Daily Case Count

This is new confirmed case count. Change the "pertainsDate" to see the case count for other days.

Daily Death Count

This is the count of deaths reported for the particular date. Change the date to see deaths for prior days.


These are counties where the 4 day new case count per capita (per 100,000 population) is significantly greater than the count per capita for the abutting counties. Because we use a 4 day case count, we are avoiding temporary spikes due to data collection delays and other abnormalities.

Case growth per capita

This is the increase in cases per 100,000 population over the most recent four days.

Average four-day death rate

This is the average death rate per capita over the most recent four days.

Average death rate per 100K


These are counties where the death rate is climbing or is steady.


These are counties where the death rate is falling.

Pertains date

This is the date that is currently displayed.

Display scale

This controls the color displayed for a specific county. While "Linear" is selected, the color chosen is linearly proportional to the value of the selected county compared to the difference between the minimum and maximum values. While "log" is selected, the color chosen is instead proportional to the decimal logarithm of the value.

This data is heavily concentrated, so that a very small number of counties have very high values, and a very large number of counties have small values. Selecting "linear" makes it easier to see the counties where the value is highest (colored in red). Selecting "log" makes it possible to see the differences among counties with low values.

The caret (small black diamond) shows the relative position in the scale of the color of the county under the current mouse location.

Analysis Results/Edge Intensity

The COVID data browser technology stack runs a suite of analysis tools that are applied to whatever data is in the database (including the results other analysis tools). The first of these computes a value of "Edge Intensity" for whatever is being shown on the map.

The results of each analysis tool are displayed by clicking the named control.

Edge Intensity

The "edge intensity" of a county is highest when that county is at a boundary between neighbors whose value is high and those whose value is low. Since, like weather, COVID is a geographic phenemenon, these boundaries are analogous to warm and cold fronts on a weather map.

Counties with a high edge intensity for a particular variable are more likely to experience a change in that variable in the immediate future than counties with a low edge intensity. A sequence of edge intensity maps over several days provides guidance about the rate at which a local event is spreading or shrinking.