Novel coronavirus 2019-nCoV (COVID-19): early estimation of epidemiological parameters and epidemic size estimates

Abstract

Since it was first identified, the epidemic scale of the recently emerged novel coronavirus (2019-nCoV) in Wuhan, China, has increased rapidly, with cases arising across China and other countries and regions. Using a transmission model, we estimate a basic reproductive number of 3.11 (95% CI, 2.39-4.13), indicating that 58-76% of transmissions must be prevented to stop increasing. We also estimate a case ascertainment rate in Wuhan of 5.0% (95% CI, 3.6-7.4). The true size of the epidemic may be significantly greater than the published case counts suggest, with our model estimating 21 022 (prediction interval, 11 090-33 490) total infections in Wuhan between 1 and 22 January. We discuss our findings in the light of more recent information. This article is part of the theme issue 'Modelling that shaped the early COVID-19 pandemic response in the UK'.

Keywords: China; SARS-CoV-2; ascertainment rate; international travel; pandemic; transmission model.

Figure 1.

Connectivity of Wuhan to other cities and provinces in mainland China, based on total commercial airline traffic from Wuhan in January 2017. Traffic is based on the number of departing bookings. (Online version in colour.)

Figure 2.

Sensitivity of parameter estimates to the assumed latent period (1/α) value. Boxes represent the 2.5% and 97.5% quantiles and black dots the 50% quantile. (a) Basic reproductive number, (b) transmission rate, (c) recovery rate, (d) infections, 1 January, and (e) case ascertainment ratio. (Online version in colour.)

Figure 3.

(a) Comparison of observed cases and predicted cumulative confirmed cases in Wuhan for the period 1–24 January. Out-of-scope epidemic predictions of cumulative confirmed cases for (b) Hubei, (c) Beijing, (d) Guangzhou and (e) Shanghai up to 29 January. Grey region denotes the prediction period; 95% confidence intervals around the mean epidemic trajectories are denoted by coloured areas.

Figure 4.

Out-of-scope predictions of cumulative confirmed cases in selected countries/regions up to 29 January. Grey region denotes the prediction period; 95% confidence intervals around the mean epidemic trajectories are denoted by coloured areas. (a) Hong Kong SAR, (b) Japan, (c) Malaysia, (d) Singapore, (e) South Korea, (f) Taiwan, (g) Thailand and (h) USA. (Online version in colour.)