COVID-19 Epidemic Outside China: 34 Founders and Exponential Growth

Yi Li; Meng Liang; Xianhong Yin; Xiaoyu Liu; Meng Hao; Zixin Hu; Yi Wang; Li Jin

Recently, many researchers devoted to more details about the analysis of the spread of epidemic. 14,15 Some paralleled results have shown that the reproductive number R0 estimated of COVID-19 is bigger than that of SARS based on different models. [16] [17] [18] With the limited number of data points and the complexity of the real situation, a straightforward model is expected to work better (see Discussion). In this study, we propose a "log-plus" model for the situation prediction which only requires daily number of total diagnosis outside China. This model assumes that there were some unobserved founder patients at the beginning of spread outside China and exponential growth later. Despite the simplicity of our model, it fits the data well (R 2 =0.991). The prediction is expected to provide practical significance on social application and evidence for enhancing public health interventions to avoid severe outbreaks.