The transmission of the Black Death to western Europe: a critical review of the existing evidence

In 1347 the Black Death was introduced from the north-eastern coast of the Black Sea and the Sea of Asov towards southern and western Europe, where it then spread dramatically. A report by the Italian chronicler Gabriel de Mussis of the siege of Caffa (1345–47) is often credited as describing an early deployment of a “biological weapon”, thus triggering the “Black Death” in western Europe. He reports that Mongol troops threw plague victims into the city with catapults, thus contaminating the inhabitants. However, re-evaluation of historical, biological and epidemiological data indicates that the spread of the disease was probably an inevitable consequence of the intense trade relations along the coasts of the Black Sea and the Mediterranean. Therefore, the alleged catapulting of infected corpses would rather have been a marginal contribution to the diffusion of the disease (if it took place at all). The infection was subsequently spread by refugee ships via ports at Constantinople and along the Mediterranean trading routes and harbours towards Genoa, Marseille and Venice, thus initiating the Plague in Europe. The further propagation of the disease inland is still a matter of controversial discussions. However, epidemiological data indicate that the most essential animal vector for further distribution of the plague in central and northern Europe was probably the human louse (Pediculus humanis), instead of the oriental (or tropical) rat flea (Xenopsylla cheopis).