Quantifying the association between domestic travel and the exportation of novel coronavirus (2019-nCoV) cases from Wuhan, China in 2020: a correlational analysis

Abstract

In the end of 2019, a novel coronavirus (2019-nCoV) emerged in Wuhan, China and was causing a serious outbreak of acute respiratory illness. ¹ Wuhan locates in the centre of mainland China with a population of 14 million and is very conveniently connected to other parts of China through airlines and high-speed rails. ² As of 31 January 2020 (5:00 p.m., GMT + 8), there were 9809 confirmed 2019-nCoV cases in mainland China, including 213 deaths and 180 discharges. ^{3, 4} Cases infected in Wuhan were also detected in many foreign countries or regions including Thailand, Japan, Republic of Korea, the United States, Canada and some European countries. ⁴ The World Health Organization (WHO) has declared that the novel coronavirus outbreak is a public health emergency of international concern. Official reports on the newly confirmed cases are released very rapidly (several times a day) after January 16, ^3–5 as the official diagnosis protocol was released by the WHO on January 17. ⁶ Recent studies indicated the likelihood of travel-related risks of 2019-nCoV spreading both domestically and internationally. ^{7, 8} Many major cities in mainland China reported the finding of imported cases, including Beijing, Shanghai, Guangzhou and Shenzhen. The outbreak is still on-going with an increasing trend in daily new cases. ^{3, 4} Before the Wuhan lockdown (official travel restriction) on January 23, virtually all cases found in other major cities were exported cases from Wuhan. Population flow data between major cities in mainland China are available online due to the rapid development of internet in recent decades, see https://qianxi.baidu.com/ (in Chinese). In this work, we quantified the association between the domestic travel load and the number of cases exported from Wuhan to other city-clusters in mainland China. Our city-clusters are the pool of top five cities in the top 10 provinces (in number of cumulative cases). Thus, we included 10 city-clusters in the analysis, and the details of the selected city-clusters can be found in Supplementary Data S1 .