The Black Death (the medieval Black Plague) is believed to have originated in Asia, with strongest recent evidence pointing to Central Asia near what is now Kyrgyzstan, in the region around the Tien Shan mountains and the Chüy Valley. From there, genetic and historical data indicate the plague strain that would become the Black Death diverged and spread westward along trade routes, reaching Crimea (notably the port of Kaffa) by the mid-1340s and then moving into Europe via Mediterranean trade networks and overland routes, fueling the pandemic that swept Europe between roughly 1347 and 1351.