How it began
Ragusa, the Adriatic merchant republic now called Dubrovnik in Croatia, was hit by the Black Death in 1348. On July 27, 1377, its Great Council passed a law titled Veniens de locis pestiferis non intret Ragusium vel districtum, meaning that those arriving from plague-infected areas shall not enter Ragusa or its district. Arrivals had to spend 30 days in isolation, a period recorded as trentine, on the uninhabited island of Mrkan or in the town of Cavtat. The order was copied into the city lawbook, the Liber Viridis, which survives in the Dubrovnik archives.
Before it existed
Isolation as an idea was older than the 1377 law. The Statute of the City of Dubrovnik, written in 1272, contains the first mention there of isolating patients with leprosy, and a historian quoted by the BBC says the administration arrived at quarantine from that experience. Elsewhere the response to plague could be exclusion. The BBC article cites an account of discrimination against ships and travelers from certain countries in Venice.
How it works
Anyone arriving from a plague-stricken place was stopped and held apart for 30 days, later extended to 40, before entering the walled city. Ships anchored off the coast so that crews and goods could be watched, and residents were barred from visiting them. The first quarantine quarters were improvised huts, tents or the open air, and huts could be burned afterward as disinfection. To detain people who looked healthy, the councillors had to accept that a disease might incubate unseen, roughly five centuries before germ theory.
Who pushed back
The law was a risk for a republic that lived on trade. Ragusa's rocky soil could not feed its people, so grain came by ship from Sicily and the Levant, and plague often came with it. Closing the harbor was not an option. A paper in Medicina nei secoli argues that the four-week stay arose mainly from the need to protect the commercial network and merchandise. Offenders faced strict punishments and fines.
What changed first
The city set up its first recorded Health Office, patrol boats that visited the quarantine island, and officials who traced the sick and their contacts. Britannica states that Ragusa then passed 44 years without the plague and recovered from outbreaks that devastated other regions. The system was running before Milan laid its first sanitary cordon in 1400 and before Venice opened its first plague hospital in 1423.
Where it stands today
The practice spread and the word quarantine, from the Italian for forty, followed the longer 40-day period. Quarantine buildings across Europe came to be called lazarettos. The Lazarettos of Dubrovnik still stand outside the old walls and are used as a cultural site, and the BBC reported on them in 2020 as a reminder of the city's early public health rules during the COVID-19 pandemic.
