Black Death Rewritten: Kyrgyz Plague Graves, Caffa and Human Fleas

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The people who lived through it called it the great pestilence or magna mortalitas; the name Black Death entered English only in 1755, from a Danish phrase. Plague DNA recovered from the teeth of 18 hunter-gatherers near Lake Baikal in Siberia, reported in the journal Nature, pushes Yersinia pestis in humans back 5,500 years, probably spread by handling marmots. In 2022 researchers studying graves dated 1338 and 1339 in the Chüy Valley near Lake Issyk-Kul in Kyrgyzstan, whose Syriac tombstones cite pestilence, found the direct ancestor of the strain that would sweep Europe. In 1345 the Golden Horde under Jani Beg besieged the Genoese port of Caffa in Crimea and, by tradition, catapulted plague corpses over the walls, though infected rats were likely the real carriers.

Fleeing galleys reached Constantinople in summer 1347 and Sicily that October, then Genoa, Venice and Pisa, while places off the trade routes, such as isolated Alpine villages, were largely spared. Alexandre Yersin identified the bacterium in Hong Kong in 1894 and Paul-Louis Simond showed in 1898 that rat fleas carried it, but mathematical models suggest human fleas, body lice and pneumonic spread drove Europe's rapid death toll of 25 to 50 million. Survivors gained bargaining power as wages rose, maximum wage laws failed and abandoned farmland reforested, a carbon sink that may have helped cool the climate.

• A flea whose gut is blocked by bacterial biofilm starves, bites frantically and regurgitates plague into each new wound.
• Cairo lost 40 percent of its inhabitants within eight months.
• Jews, Romani, beggars, pilgrims and lepers were accused of poisoning wells and massacred.
• Ragusa, modern Dubrovnik, imposed 30 days of isolation on arrivals in 1377, later extended to 40, the origin of quarantine.
• Yersinia pestis still circulates in wild rodents in the western United States and Central Asia.