Order of authorship in the original paper: Baize, Pannetier, Oestereich. The authors used PCR, viral sequencing, and phylogenetic analysis to track down the index case, a two-year-old child in Meliandou village, Guékédou Prefecture, southern Guinea. This case, in which the child died on December 6, 2013, sparked the Ebola Zaire epidemic of 2014. The authors tracked down all contacts with the child to a point of unstoppable spread and dissemination. In a multi-country collaboration the virus was sequenced and characterized.

Digital facsimile from nejm.org at this link.

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