On 9 January 2020, a novel coronavirus, 2019-nCoV, was officially identified as the cause of an outbreak of viral pneumonia in Wuhan, China [11]. Wuhan is a large city of more than 11 million people located in central China around 1,200 km south of Beijing. As of 22 January, there have been 440 confirmed 2019-nCoV infections reported in 13 provinces and municipalities in mainland China and five other countries and regions overseas, with an increasing number of cases reported in recent days (Figure 1). Here, we describe the preliminary epidemiological characteristics of 2019-nCoV infections based on publicly-available information (including some media reports) before an official ‘line list’ of confirmed cases becomes available.