Identifying changes in the reproduction number, rate of spread, and doubling time during the course of the COVID-19 outbreak whilst accounting for potential biases due to delays in case reporting both nationally and subnationally in the United States of America. These results are impacted by changes in testing effort, increases and decreases in testing effort will increase and decrease reproduction number estimates respectively.

Table of Contents

Using data available up to the: 2020-09-15

Subnational estimates are available to download here and national estimates are available to download here.

See our see Methods or our paper for an explanation of how these estimates are derived.

Interactive summary



Figure 1: The results of the latest reproduction number estimates (based on estimated confirmed cases with a date of infection on the 2020-09-15) can be summarised by whether confirmed cases are likely increasing or decreasing. This represents the strength of the evidence that the reproduction number in each region is greater than or less than 1, respectively (see the methods for details). Click on a subnational area (or search) to see subnational level estimates. This interactive visualisation is powered by RtD3(Gibbs, Abbott, and Funk 2020).

National summary

Summary (estimates as of the 2020-09-15)

Estimate New confirmed cases by infection date 51326 (27282 – 80573) Expected change in daily cases Unsure Effective reproduction no. 1.02 (0.8 – 1.24) Rate of growth 0.01 (-0.05 – 0.07) Doubling/halving time (days) 132.2 (10.4 – -12.6)

Table 1: Latest estimates (as of the 2020-09-15) of the number of confirmed cases by date of infection, the expected change in daily confirmed cases, the effective reproduction number, the growth rate, and the doubling time (when negative this corresponds to the halving time). The median and 90% credible interval is shown for each numeric estimate.



Figure 2: A.) Confirmed cases by date of report (bars) and their estimated date of report. B.) Confirmed cases by date of report (bars) and their estimated date of infection. C.) Time-varying estimate of the effective reproduction number (lightest ribbon = 90% credible interval; darker ribbon = the 50% credible interval, darkest ribbon = 20% credible interval). Estimates from existing data are shown up to the 2020-09-15 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation. Uncertainty has been curtailed to a maximum of ten times the maximum number of reported cases for plotting purposes.

Regional Breakdown

Case counts by date, stratified by region, were downloaded from a publically available source curated by Johns Hopkins University (“2019 Novel Coronavirus Covid-19 (2019-nCoV) Data Repository” 2020 ; Abbott et al. 2020

Case onset dates were estimated using case counts by date of report and a distribution of reporting delays fitted to a publically available line-list of international cases (Xu et al., n.d. ; Abbott et al. 2020

Limitations

Line-list data to inform a State specific estimates of the reporting delay were not available.



Figure 3: Confirmed cases with date of infection on the 2020-09-15 and the time-varying estimate of the effective reproduction number (lightest ribbon = 90% credible interval; darker ribbon = the 50% credible interval, darkest ribbon = 20% credible interval). Regions are ordered by the number of expected daily confirmed cases and shaded based on the expected change in daily confirmedcases. The horizontal dotted line indicates the target value of 1 for the effective reproduction no. required for control and a single case required for elimination. Uncertainty has been curtailed to a maximum of ten times the maximum number of reported cases for plotting purposes.

Reproduction numbers over time in the six regions expected to have the most new confirmed cases



Figure 4: Time-varying estimate of the effective reproduction number (lightest ribbon = 90% credible interval; darker ribbon = the 50% credible interval, darkest ribbon = 20% credible interval) in the regions expected to have the highest number of new confirmed cases. Estimates from existing data are shown up to the 2020-09-15 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation.



Figure 5: Confirmed cases by date of report (bars) and their estimated date of infection (lightest ribbon = 90% credible interval; darker ribbon = the 50% credible interval, darkest ribbon = 20% credible interval) in the regions expected to have the highest number of new confirmed cases. Estimates from existing data are shown up to the 2020-09-15 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation. Uncertainty has been curtailed to a maximum of ten times the maximum number of reported cases for plotting purposes.



Figure 6: Confirmed cases by date of report (bars) and their estimated date of report (lightest ribbon = 90% credible interval; darker ribbon = the 50% credible interval, darkest ribbon = 20% credible interval) in the regions expected to have the highest number of new confirmed cases. Estimates from existing data are shown up to the 2020-09-15 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation. Uncertainty has been curtailed to a maximum of ten times the maximum number of reported cases for plotting purposes.

Reproduction numbers over time in all regions



Figure 7: Time-varying estimate of the effective reproduction number (lightest ribbon = 90% credible interval; darker ribbon = the 50% credible interval, darkest ribbon = 20% credible interval) in all regions. Estimates from existing data are shown up to the 2020-09-15 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The horizontal dotted line indicates the target value of 1 for the effective reproduction no. required for control. The vertical dashed line indicates the date of report generation.

Figure 8: Confirmed cases by date of report (bars) and their estimated date of infection (lightest ribbon = 90% credible interval; darker ribbon = the 50% credible interval, darkest ribbon = 20% credible interval) in all regions. Estimates from existing data are shown up to the 2020-09-15 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation. Uncertainty has been curtailed to a maximum of ten times the maximum number of reported cases for plotting purposes.

Figure 9: Confirmed cases by date of report (bars) and their estimated date of report (lightest ribbon = 90% credible interval; darker ribbon = the 50% credible interval, darkest ribbon = 20% credible interval) in all regions. Estimates from existing data are shown up to the 2020-09-15 from when forecasts are shown. These should be considered indicative only. Estimates based on partial data have been adjusted for right truncation of infections. The vertical dashed line indicates the date of report generation. Uncertainty has been curtailed to a maximum of ten times the maximum number of reported cases for plotting purposes.

Latest estimates (as of the 2020-09-15)

“2019 Novel Coronavirus Covid-19 (2019-nCoV) Data Repository.” 2020. Johns Hopkins CSSE. https://github.com/CSSEGISandData/COVID-19. Abbott, Sam, Katharine Sherratt, Jonnie Bevan, Hamish Gibbs, Joel Hellewell, James Munday, Patrick Barks, Paul Campbell, Flavio Finger, and Sebastian Funk. 2020. “Covidregionaldata: Subnational Data for the Covid-19 Outbreak.” - - (-): –. https://doi.org/10.5281/zenodo.3957539. Gibbs, Hamish, Sam Abbott, and Sebastian Funk. 2020. “RtD3: Rt Visualization in D3.” Zenodo - (-): –. https://doi.org/10.5281/zenodo.4011841. Xu, Bo, Bernardo Gutierrez, Sarah Hill, Samuel Scarpino, Alyssa Loskill, Jessie Wu, Kara Sewalk, et al. n.d. “Epidemiological Data from the nCoV-2019 Outbreak: Early Descriptions from Publicly Available Data.” http://virological.org/t/epidemiological-data-from-the-ncov-2019-outbreak-early-descriptions-from-publicly-available-data/337.

Table 2: Latest estimates (as of the 2020-09-15) of the number of confirmed cases by date of infection, the effective reproduction number, the rate of growth, and the doubling time (when negative this corresponds to the halving time) in each region. The median and 90% credible interval is shown.