A lazaretto or lazaret is a quarantine station for maritime travellers. Lazarets can be ships permanently at anchor, isolated islands, or mainland buildings. Between 1348 and 1359 the Black Death wiped out an estimated 30% of Europe's population, as well as a significant percentage of Asia's population. The original document from 1377, which is kept in the Archives of Dubrovnik, states that before entering the city, newcomers had to spend 30 days (a trentine) in a restricted location (originally nearby islands) waiting to see whether the symptoms of plague would develop. Later on, isolation was prolonged to 40 days and was called quarantine.
Venice took the lead in measures to check the spread of plague, having appointed three guardians of the public health in the first years of the Black Death (1348). The first lazaret was founded by Venice in 1403, on a small island adjoining the city – the island of Santa Maria di Nazareth (also known as Lazaretum or Nazaretum). Today this island is known as the Lazzaretto Vecchio.
Originally, the “Lazzaretto Vecchio” was home to hermits who had erected a church dedicated to St. Mary of Nazareth and a shelter for pilgrims going or returning from the Holy Land (c.1240s). When the monks and novices died out, and on the advice of San Bernardino of Siena, the Senate voted to allocate the island as a shelter for people and goods from infected countries.
The Lazzaretto even then consisted of two islands joined by a bridge to the smallest housed the garrison whilst the larger housed the hospital which incorporated the original monastic buildings. Originally built of timber, these would be later rebuilt in stone. In 1468, the Lazzaretto Nuovo or new settlement was established. The Lazzaretto was enlarged with the adjacent lagoon being reclaimed in 1580s; and a boathouse entrance was built from the canal (1586).
In November, 1631, the plague was definitively eradicated, but at a terrible cost: almost 47,000 died in the city (more than a quarter of the population) and 95,000 in the area comprising Murano, Malamocco and Chioggia.
I was inspired to find out more from this article that appeared in the Independent in 2007:
Archaeologists are now exploring "the graves of Lazzaretto, an island in the Venetian lagoon which became the world's first isolation hospital."
The Independent reports that: "Following an outbreak of the plague in 1348, the Doge and his advisers put their minds to thinking up a way to prevent a recurrence. The upshot, at the beginning of the 15th century, was the world's first isolation hospital occupying the entire small island."
" .. archaeologists have uncovered more than 1,500 skeletons of Lazzaretto patients. Luigi Fozzatti, who is in charge of excavations, said: "It wasn't difficult to imagine that some people would have been buried on the island but we had no idea we would find so many." "
Research is continuing.