This article was published in Nature on 3 February 2020. Prior to that a version with a different title and numerous other co-authors was published in bioRxiv on 23 January 2020, as "Discovery of a novel coronavirus associated with a recent pneumonia outbreak in humans and its potential bat origin". The publication date of  23 January 2020 makes this paper the earliest scientific paper  published in a Western language describing the COVID-19 pandemic.

Order of authorship in the original publication: Zhou, Yang, Zheng. 

Abstract of the paper as it appeared in Nature on 3 February 2020:

"Since the outbreak of severe acute respiratory syndrome (SARS) 18 years ago, a large number of SARS-related coronaviruses (SARSr-CoVs) have been discovered in their natural reservoir host, bats 1,2,3,4. Previous studies have shown that some bat SARSr-CoVs have the potential to infect humans 5,6,7. Here we report the identification and characterization of a new coronavirus (2019-nCoV), which caused an epidemic of acute respiratory syndrome in humans in Wuhan, China. The epidemic, which started on 12 December 2019, had caused 2,794 laboratory-confirmed infections including 80 deaths by 26 January 2020. Full-length genome sequences were obtained from five patients at an early stage of the outbreak. The sequences are almost identical and share 79.6% sequence identity to SARS-CoV. Furthermore, we show that 2019-nCoV is 96% identical at the whole-genome level to a bat coronavirus. Pairwise protein sequence analysis of seven conserved non-structural proteins domains show that this virus belongs to the species of SARSr-CoV. In addition, 2019-nCoV virus isolated from the bronchoalveolar lavage fluid of a critically ill patient could be neutralized by sera from several patients. Notably, we confirmed that 2019-nCoV uses the same cell entry receptor—angiotensin converting enzyme II (ACE2)—as SARS-CoV."

Open access from nature.com at this link.