As of January 25th, 2020 (Beijing time), China has reported 1409 confirmed cases, 2032 suspected cases, and 42 deaths of 2019 Novel Coronavirus (2019-nCoV) infections, with most reported from Wuhan city, Hubei Province [1-3]. Nearly all provinces have confirmed imported cases from Wuhan and secondary transmission has been reported in some provinces. The spread of the virus could have been exacerbated by the surge in domestic travel during the 40-day Lunar New Year celebrations (from 10 January to 18 February 2020) – the largest annual human migration in the world, comprised of hundreds of millions of people travelling across the country.

We used de-identified and aggregated domestic population movement data from 2013 to 2015, derived from Baidu Location-Based Services (LBS) [4], and international air travel data in 2018, obtained from the International Air Transport Association (IATA) [5], to explore patterns of mobility of travellers from Wuhan to other cities in China, and inform the risk of 2019-nCoV spreading across and beyond the country during the Lunar New Year migration.

Using the 2013-2015 LBS data, we found that a large number of travellers were likely departing Wuhan into neighbouring cities and other megacities in China before Lunar New Year (Figures 1-3 and Tables 1-3). There was a high correlation between the number of imported cases and the risk of importation via travellers from Wuhan within the two weeks before Lunar New Year’s Day (Figure 4). Further, a high proportion of cases travelled with symptoms at the early stage of the outbreak. Although a cordon sanitaire of Wuhan and some cities in Hubei Province has been in place since January 23rd, 2020, the timing of this may have occurred during the latter stages of peak population numbers leaving Wuhan (Figure 1). Should secondary outbreaks occur in the cities and provinces that receive high volumes of travellers from Wuhan, e.g. Beijing, Shanghai, and Guangzhou, these could contribute to further spread of infection to other highly connected cities within China via movement after the 7-day public holiday (Figures 5-7). Additionally, based on historical air travel data, the connectivity between high-risk cities in China and other countries was defined for the three months around Lunar New Year holiday (Tables 4 and 5). We have initially focussed on specific destination cities in Africa due to the weak surveillance and health systems of this vulnerability region (Tables 6-7 and Figures 8-9), but will expand similar assessments to the rest of the World.

Given the current epidemic and limited understanding of the epidemiology of this disease, our findings of travel patterns from historical data could help contribute to tailoring public health interventions. However, it is important to highlight that our analysis assumes “business as usual” travel based on previous non-outbreak years and we are currently in unprecedented territory, with likely significant changes to human travel behaviours across China. We are closely monitoring the epidemic, and further analyses will be conducted to estimate the risk of onward domestic and international spread of the virus during the Lunar New Year and the next few months. Moreover, we will also attempt to evaluate the effectiveness of the transport lockdown in Chinese cities, and the impact of movements of people returning from holiday on the transmission of the 2019-nCoV virus.

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