Using the viral genome isolated from the archival serum of the "Kinshasa patient", Lemey, Faria and colleagues deduced that the prototype African viral strain first crossed from monkeys to humans about 1920 in the area of Kinshasa in Africa. This was about forty years before it was first detected in a stored human blood sample collected in 1959 from a hospitalized patient it in Kinshasa. Order of authorship in the original publication was Faria, Rambaut, Suchard...Lemey.
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(Thanks to Juan Weiss for this reference and its interpretation.)