Venice's permanent plague hospital, the Lazaretto

Plague kept returning to Venice after the Black Death struck the city in the mid-14th century, and as a trading center Venice was especially exposed. At first the sick had been separated from the healthy in makeshift camps, and Ragusa (Dubrovnik) had introduced quarantine in 1377. In 1423 the Republic of Venice opened a permanent hospital for plague patients on the small island of Santa Maria di Nazareth.

The hospital was commonly called Nazarethum or Lazarethum, because the word lazaretto resembled the biblical name Lazarus. It was later known as the Lazzaretto Vecchio. Its few surviving buildings show that it was a base for treating the infected, and sick Venetians were generally sent there.

In 1468 a government decree gave a second island, then home to a monastery, to a new isolation hospital, the Lazzaretto Nuovo. Ships arriving from places with plague, or carrying suspected cases, anchored there, and people and cargo waited out a quarantine before entering the city. Records describe warehouses and more than 100 rooms for sailors and crews. Armed guards and porters unloaded cargo into the largest warehouse, the Tezon Grande, which still stands. Goods were aired and cleared with the smoke of aromatic herbs and with saltwater, and the workers washed their hands in vinegar.

Genoa adopted the Venetian system in 1467, and in 1476 Marseille turned a leprosy hospital into a lazaretto. Such hospitals were placed far enough from town to limit spread but near enough to carry the sick there, behind the sea or a river where possible and otherwise behind a moat or ditch. Venice kept its permanent, government-run system, which employed hundreds of officials, until Napoleon conquered the region in 1797.

Plague still got through. An outbreak in 1630 killed about a third of the people of Venice and Bologna. In recent decades archaeologists have found mass graves on both islands. On the Lazzaretto Nuovo, where the overwhelmed city also sent the sick and the dead during epidemics, the forensic anthropologist Matteo Borrini studied about 200 bodies in graves that had been reopened again and again. Their bones show the diets of wealthy, middle-class and poor Venetians alike.