Amidst the continuing spread of the COVID-19 pandemic, timely, data-driven metrics remain critical to track the pandemic's impact and inform policy making. It is critical to use multiple metrics concurrently as they provide complementary insight into relative impact, as in the effective reproduction number (Rt), and absolute impact, as in the number of new cases and deaths in a given population. This tool provides a visualization for these three metrics which are calculated based on Poisson log-linear models. Please see the About tab for more information about the usage of the site and please see our paper for more details about the method.

  • The effective reproduction number (Rt) characterizes the COVID-19 spread rate, defined as the average number of secondary infectious cases produced by a primary infectious case. It's used to define the potential for spread at a specific time. If Rt > 1, the virus will spread out and the disease will become an epidemic; if Rt = 1, the virus will spread locally and the disease is endemic; if Rt < 1, the virus will stop spreading and the disease will disappear eventually.

  • The daily new cases per million and daily new deaths per million quantify the daily new COVID-19 cases and deaths, scaled by the population of a given area.

Change the date, metric, and resolution below. Click on an area in the map to see its metrics over time.

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Select areas to compare their Rt.

Some areas may not appear in the plot for all time points because of insufficient data.

Occasionally, locations may have negative values for observed new daily cases or new daily deaths because of reporting issues.

Some overseas possessions, like Bermuda or French Polynesia, can be found in the Countries selector, not the Subnational one.

Note the Rt is lagged by 7 days.

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Click a column to sort by that metric. Note that Rt is not available beyond Sat October 16, 2021 due to the 7 day lag.


The Rt, case rate, and death rate might also not be shown for certain locations and certain dates if that location had too few total cases or too few new cases on that date. Occasionally, locations may have negative values for new cases or new deaths because of reporting issues. Full table available for download on Github.

Table Column Explanations

  • Location: Location name as a string.
  • Rt, Rt (lwr), Rt (upr): Value of Rt and the lower and upper 95% confidence interval bounds, calculated using the Poisson method. Note that there is a 7-day lag for Rt, so there are no estimates of Rt or its confidence interval in the last 7 days of the data.
  • Case rate, Case rate (lwr), Case rate (upr): Value of the case rate per million population and the lower and upper 95% confidence interval bounds, calculated using the Poisson method.
  • Death rate, Death rate (lwr), Death rate (upr): Value of the death rate per million population and the lower and upper 95% confidence interval bounds, calculated using the Poisson method.
  • Cum. cases: Cumulative number of cases up to and including the date selected.
  • Daily new cases: Number of new COVID-19 cases on the date selected. Note that different locations may define a case differently, e.g. some may only include those confirmed by PCR tests, while others would include those who tested positive on an antibody test and had COVID-19 symptoms.
  • Cum. cases per million: Number of cumulative cases up to and including the date selected per million population. We used the population numbers from the JHU CSSE data to calculate any per capita statistics.
  • Daily new cases per million: Number of new COVID-19 cases on the date selected per million population. Note that different locations may define a case differently, e.g. some may only include those confirmed by PCR tests, while others would include those who tested positive on an antibody test and had COVID-19 symptoms.
  • Cum. deaths: Cumulative number of deaths up to and including the date selected. Note that different locations may define a COVID-19 death differently.
  • Daily new deaths: Number of new COVID-19 deaths on the date selected. Note that different locations may define a COVID-19 death differently.
  • Cum. deaths per million: Cumulative number of deaths up to and including the date selected per million population.
  • Daily new deaths per million: Number of new deaths on the date selected per million population.
  • Population: Population of the location from the JHU CSSE data used to calculate any per capita statistics.

Website Usage

Map tab: This tab shows a map of the Rt, case rate, or death rate by date for various resolutions. Change the date by clicking on the displayed date and using the calendar. Change the geographic resolution (country, states / subnational, US states' counties) using the resolution dropdown menu, and click on a location on the map to see a line graph of the Rt, case rate, and death rate over time. In this plot, the dotted line shows the observed number of new cases or deaths per day, while the solid line and gray band shows the calculated Rt, case rate, or death rate along with a 95% confidence interval. You can scroll to change the zoom of the map and click-drag to move the map around. Locations where Rt, case rate, or death rate could not be calculated are shown as gray in the map (see Limitations for more info).

By clicking “Show More”, a heatmap and forest plot will be displayed. The heatmap shows the values of the selected metric as colored blocks over time in the selected geographic resolution. The forest plot shows the estimated value (as a point) and 95% confidence interval (as a bar) of the selected metric on the selected day. Locations where the metric could not be calculated are shown as gray in the heatmap and not shown in the forest plot (see Limitations for more info).

Compare tab: Select states / provinces / subnational units, US counties, and countries to compare their Rt over time. You can select a location by using the dropdown menu. You can also type the name of the location. Multiple locations for each category (states, counties, and countries) can be chosen. Additionally, choose which metrics to display and toggle display of the confidence interval for the Rt, case rate, and death rate. After you click submit, the results will be displayed as a series of line plots. Some areas may not appear in the plot because of insufficient data (see Limitations for more info).

Table tab: This tab shows a table of Rts for the chosen date and resolution, as well as the number of new cases, new case rate, cumulative number of cases, number of new deaths, new death rate, and cumulative number of deaths. The columns displayed in the table can be changed by clicking the dialog box under “Select Columns for Table”. Click the “Reset Columns” button to reset the columns to the default configuration, and click the “Download Table” button to download the table as a csv file. This table is by default sorted in descending order of case rate, but the sorting can be changed by clicking a column header. Locations where Rt could not be calculated are not shown in the table (see Limitations for more info).

Downloading Plots / Maps / Rt

To download a plot, you can use the Download buttons, or alternatively right-click on a plot and select “Save Image As…” Right now we do not have a way to save a map, but in the meantime you can take a screenshot. To download the information shown in the tables, please see the Rt table CSV on our Github page or use the Table tab.

If you'd like the shapefiles with metrics information merged that we used for our maps, they are saved as an RDS file on our Github.

Method Description

We calculate and report the daily effective reproduction number (Rt), case rate, and death rate to characterize the COVID-19 spread rate. The Rt is defined as the expected number of secondary infectious cases produced by a primary infectious case. Rt is used to determine the potential for epidemic spread at a specific time t under the control measures in place (Figure 1, Inglesby, T.V., 2020, reproduced below). If Rt > 1, the virus will spread out and the disease will become an epidemic; if Rt = 1, the virus will spread locally and the disease is endemic; if Rt < 1, the virus will stop spreading and the disease will disappear eventually.