Prediction of the Epidemic Peak of Coronavirus Disease in Japan, 2020

Abstract

The first case of coronavirus disease 2019 (COVID-19) in Japan was reported on 15 January 2020 and the number of reported cases has increased day by day. The purpose of this study is to give a prediction of the epidemic peak for COVID-19 in Japan by using the real-time data from 15 January to 29 February 2020. Taking into account the uncertainty due to the incomplete identification of infective population, we apply the well-known SEIR compartmental model for the prediction. By using a least-square-based method with Poisson noise, we estimate that the basic reproduction number for the epidemic in Japan is R 0 = 2 . 6 ( 95 % CI, 2 . 4 - 2 . 8 ) and the epidemic peak could possibly reach the early-middle summer. In addition, we obtain the following epidemiological insights: (1) the essential epidemic size is less likely to be affected by the rate of identification of the actual infective population; (2) the intervention has a positive effect on the delay of the epidemic peak; (3) intervention over a relatively long period is needed to effectively reduce the final epidemic size.

Keywords: COVID-19; SEIR compartmental model; basic reproduction number.

Figure 1

Comparison of $Y\left(t\right)$ with the estimated infection rate $\beta$ and the number of daily reported cases of COVID-19 in Japan from 15 January ($t=0$) to 29 February ($t=45$).

Figure 2

Time variation of the number $Y\left(t\right)$ of infective individuals who are identified at time t ($0\le t\le 365$) for $p=0.1$. The dot lines represent the epidemic peak $t^{*}$.

Figure 3

Time variation of the number $Y\left(t\right)$ of infective individuals who are identified at time t ($0\le t\le 365$) for $p=0.01$. The dot lines represent the epidemic peak $t^{*}$.

Figure 4

Time variation of the number $Y\left(t\right)$ of infective individuals who are identified at time t ($0\le t\le 365$) for $p=0.01$ and no intervention, 1 month intervention ($T=77$) and 6 months intervention ($T=220$). The dot lines represent the epidemic peak.

Figure 5

The relation between the planned final day for intervention T and (a) the epidemic peak $t^{*}$; (b) the number of accumulated cases at time $t=365$: $pR\left(365\right)\times 1.26\times {10}^8$.