Strongly heterogeneous transmission of COVID-19 in mainland China: local and regional variation

Yuke Wang; Peter F.M. Teunis

Outside Hubei there was less transmission than within Hubei province, with average reproduction numbers between 1 and 2 during the first five days after the first confirmed local case. The provinces Guizhou, Hebei, Shandong, and Guangdong had higher average reproduction numbers: 2·25, 2·14, 1·95, and 1·91, respectively (Figure 4a ). Though the average reproduction numbers were not very high, there existed large variations in reproduction numbers of individual cases, which indicated some individual cases could have spread the disease to many people ( Figure 2 ). Within a province, there was also spatial variation in the amount of transmission. Figure 5 shows the disease transmission in 21 cities within Guangdong province. Shenzhen and Guangdong, the two largest and most affluent urban centers in Guangdong, had the highest estimated numbers of cases imported from Wuhan (127 and 124, respectively) by 3 February 2020. Guangzhou, Zhaoqing, Shaoguan, Shenzhen, and Zhuhai had reproduction numbers slightly larger than 1 (1·35, 1·31, 1·30, 1·10 and 1·05, respectively) for first five days after the first confirmation of a local case in the city. Figures A1 and A2 show boxplots of estimated reproduction numbers for provinces in China and cities in Guandong province, respectively. Figure A3 shows reproduction number estimates by gender and age for Beijing and Tianjin.