Preliminary Assessment of Chinese Strategy in Controlling Reemergent Local Outbreak of COVID-19

Abstract

Reemergent local outbreaks of coronavirus disease 2019 (COVID-19) have occurred in China, yet few Chinese response strategies and its evaluation have been reported. This study presents a preliminary assessment of Chinese strategy in controlling reemergent local outbreaks of COVID-19. Time course of accumulative and daily new cases and time-varying reproductive numbers (Rt) of outbreak areas were presented. The asymptomatic rate, days required to control the outbreaks, seeding time (ST), and doubling time (DT) of areas with over 96 reemergent cases were calculated. National and local year-on-year growth rates of gross domestic product (GDP) were presented. Accumulative numbers of 30, 8, 11, 430, 15, 139, 1,067, 382, 42, and 94 confirmed reemergent COVID-19 cases were diagnosed in Hulun Buir, Shanghai, Tianjin, Kashgar, Qingdao, Dalian, Urumchi, Beijing, Jilin, and Harbin, respectively. Among them, maximum rate of asymptomatic infections was 81.9%. Time required to control the local outbreaks in the areas given above varied from 29 to 51 days. After activation of outbreak responses, the late-stage DTs of Kashgar, Urumchi, Beijing, and Dalian were apparently lengthened compared to the early-stage DTs. Although the year-on-year GDP growth rate of Urumchi was slightly affected, the GDP growth rate of Dalian, Beijing, Jilin, and Harbin kept rising during the reemergence. Moreover, the year-on-year GDP growth rate of Mainland China turned positive regardless of the reemergent local outbreaks. In general, the Chinese strategy to maintain the status of no or minimal transmission was effective in balancing the control of COVID-19 reemergent local outbreak and the recovery of economy.

Keywords: COVID-19; China; GDP; SARS-CoV-2; asymptomatic infection; reemergent local outbreak.

Figure 1

Daily new symptomatic and asymptomatic cases and time-varying reproductive numbers (Rt) curve in reemergent areas. Bar graphs present daily new cases of the local reemergent outbreaks in Hulun Buir (A), Shanghai (B), Tianjin (C), Kashgar (D), Qingdao (E), Dalian (F), Urumchi (G), Beijing (H), Jilin (I), and Harbin (J). Rt curves of reemergent areas are shown on the upper right part of each bar graph, respectively. Cases with identical origin as the originating site were counted together in the originating site cases. Rt stands for time-varying reproductive number.

Figure 2

Time course of the accumulated number of confirmed cases in reemergent areas. This epidemiological curve shows an accumulative number of confirmed cases of Hulun Buir, Shanghai, Tianjin, Kashgar, Qingdao, Dalian, Urumchi, Beijing, Jilin, and Harbin. The curve was presented by day, from the day the 1st case was reported to the 14th day with no new case reported. People who presented with asymptomatic infection at first but later developed clinical syndrome were excluded from the asymptomatic cases.

Figure 3

Seeding time (ST) and doubling time (DT) of Kashgar, Dalian, Urumchi, and Beijing reemergent outbreaks. This scatter diagram shows ST and DT1~6 of Kashgar, Dalian, Urumchi, and Beijing reemergent outbreaks. The time interval between the date of the first reported case and the date of a number of cases reaching the median seeding number (SN) of an area (median SN = 12 according to the study of Zhou L) was defined as ST. DT was the time interval required to double the accumulative number of cases of an area. DT1 ~ DT6 were calculated according to the time interval between the 12 and 24, 24 and 48, 48 and 96, 96 and 192, 192 and 384, and 384 and 768 confirmed cases, respectively. ST stands for seeding time. DT stands for doubling time.

Figure 4

National and local year-on-year GDP growth rate. This bar graph presents the year-on-year GDP growth rate of Mainland China and the local year-on-year GDP growth rates of Dalian, Urumchi, Beijing, Jilin, and Harbin of 2018, 2019, and the first three quarters of 2020. GDP stands for gross domestic product.