question: In April 2013, severe porcine epidemic diarrhea (PED) outbreaks first appeared in USA, causing significant financial losses. To detect the geographic origin and timing of USA porcine epidemic diarrhea virus (PEDV) isolates, we conducted a retrospective study to isolate 19 PEDV strains from positive samples obtained prior to April 2013. The results of phylogenetic and recombination analyses showed that GDS10 strain shared a common ancestor with CO13 strain, which was obtained from a piglet with severe diarrhea in USA.