Dated October 28, 2005, roughly two years after the outbreak of SARS, the natural reservoirs of this class of coronaviruses was discovered.

(Thanks to Juan Weiss for this entry and its interpretation.)

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.