Estimating the reproductive number and the outbreak size of COVID-19 in Korea

Abstract

Objectives: Since the first novel coronavirus disease 2019 (COVID-19) patient in Korea was diagnosed on January 20, 2020, 30 patients were diagnosed until February 17, 2020. However, 5,298 additional patients were confirmed until March 4, 2020. Therefore, our objective was to estimate the reproduction number (R) and evaluate the effectiveness of preventive measures.

Methods: A COVID-19 transmission model (SEIHR) was established to suit the Korean outbreak. The number of daily confirmed cases in Daegu and North Gyeongsang Province (NGP), the main area of outbreak, was used. The first patient' symptom onset date in the Daegu/NGP outbreak was assumed as January 22, 2020. The R according to the start date of the effect of preventive measures was estimated.

Results: The estimated R in Hubei Province, China, was 4.0281, whereas the estimated initial R in Korea was 0.555, but later in Daegu/NGP, the value was between 3.472 and 3.543. When the transmission period decreases from 4-day to 2-day, the outbreak ends early, but the peak of the epidemic increases, and the total number of patients does not change greatly. It was found that, if transmission rate decreases, the outbreak ends early, and the size of the peak and the total number of patients also decreases.

Conclusions: To end the COVID-19 epidemic, efforts to reduce the spread of the virus, such as social distancing and wearing masks, are absolutely crucial with the participation of the public, along with the policy of reducing the transmission period by finding and isolating patients as quickly as possible through the efforts of the quarantine authorities.

Keywords: COVID-19; Epidemiology; Korea; Mathematical model; Outbreak; Reproduction number.

Conflict of interest statement

The authors have no conflicts of interest to declare for this study.

Figures

Figure 1.

Deterministic SEIHR model for coronavirus disease 2019.

Figure 2.

Estimated reproductive number (R) by daily cumulative reported patients with coronavirus disease 2019 in Hubei Province, China. The number of infected patients (I0) on December 29, 2019 was assumed as 1 to 5. Cumulative number of cases (red dots) and model fitting curves (colored lines).

Figure 3.

Estimated reproductive number (R) by daily cumulative symptom onset patients with coronavirus disease 2019 in Korea from January 20, 2020 to February 17, 2020. Cumulative number of cases (red dots) and model fitting curves (colored lines).

Figure 4.

Estimated reproductive number (R) by daily cumulative confirmed patients in Daegu and North Gyeongsang Province from February 18, 2020 to March 4, 2020. The first patient was assumed to have been infected on January 22, 2020. The fite refers to the last date of the model fitting. Cumulative number of cases (red dots) and model fitting curves (colored lines). (A) fite: February 24, 2020 to February 28, 2020 (B) fite: February 29, 2020 to March 4, 2020

Figure 5.

Estimated number of cumulative confirmed patients by scenario in Daegu and North Gyeongsang Province (see Table 2 for scenarios).