Technology & Medicine › Medieval › Black Death (bubonic plague)
Quarantine
1377 (Ragusa, now Dubrovnik)· Idea, religion or movement· Germs, drugs & genetics
Well documentedSolid records, physical evidence or scientific consensus.
Holding travelers and goods apart for a set period to stop disease spreading, first made law in Ragusa (Dubrovnik) in 1377.
See it on the Technology & Medicine map →How it works
On July 27, 1377, the city-state of Ragusa ordered arrivals from plague areas to wait 30 days on a nearby island or in a town outside the walls before entering. Venice opened a permanent isolation hospital, a lazaretto, in 1423, and Venice and other ports later stretched the wait to 40 days, quaranta giorni in Italian, which gave the practice its name. Officials knew nothing of germs; they simply observed that plague followed people and cargo.
Why it mattered
It was one of the first organized public health measures enforced by governments, and it remains in use today, most visibly during COVID-19.
How we know
Ragusa's 1377 decree survives in the city's law book, the Liber Viridis; Venetian health board records and excavations on the Lazzaretto Vecchio island document later practice.
Still unknown or debated
Why 40 days was chosen is unclear: perhaps biblical symbolism, such as Lent, or the old medical idea that acute illness declares itself within 40 days.
Connections (4)
▸Ibn Sina's Canon of Medicine may have anticipated the 40 days of QuarantineDebated
The connection
Ibn Sina wrote that some diseases spread through contact and corrupted air, and he is often credited with recommending 40 days of isolation. If so, the Canon, widely taught in Italian medical schools, could have influenced the 40-day wait later adopted by Venice. The link is plausible but unproven.
When and how
The Canon was completed in Persia in 1025; Ragusa's 30-day rule came in 1377, and Venice and other Italian ports moved to 40 days in the 1400s.
How sure are we?
Uncertain: a passage clearly prescribing 40-day isolation is hard to find in the Canon, and the Italian decrees do not cite Ibn Sina.
Debates and open questions
The number 40 also had biblical meaning and appears in ancient Greek writing on acute disease, so the Canon may be one of several sources, or none.
▸Black Death (bubonic plague) led to QuarantineWell documented
The connection
After the Black Death, plague returned in new waves about every decade. Port cities trading with the eastern Mediterranean noticed that outbreaks followed arriving ships and travelers. In 1377 Ragusa ordered newcomers from infected areas to wait 30 days before entering; Venice and others copied and lengthened the rule.
When and how
Ragusa (Dubrovnik), on the Adriatic coast of today's Croatia, by decree of July 27, 1377, during a later plague wave; Venice built its first lazaretto in 1423.
How we know
Ragusa's decree survives and explicitly targets plague; later health board records across Italy describe quarantine as a plague defense.
Debates and open questions
How effective early quarantine was is debated, since rats and fleas could slip past it; isolation rules in Milan's territory in 1374 may also count as a first.
▸Quarantine was revived worldwide during the COVID-19 pandemicWell documented
The connection
Quarantine, first used by Ragusa (Dubrovnik) in 1377 to hold arrivals for 30 days against plague, rests on a simple idea: separate the possibly infected until the danger passes. In 2020 governments revived it on a vast scale, with travel quarantines, isolation of cases and city-wide lockdowns, starting with Wuhan's on January 23, 2020.
When and how
Wuhan's lockdown of about 11 million people from January 23, 2020; then lockdowns and travel quarantines across Europe, India, the Americas and Asia, 2020–22.
How we know
Government orders and travel rules are fully documented; studies of phone mobility data show how sharply movement dropped.
Debates and open questions
How many lives lockdowns saved, weighed against their economic, educational and mental-health costs, is still debated; studies differ by country and timing.
▸Quarantine was challenged, then refined, by the Sanitation and public health movementMostly agreed
The connection
Quarantine isolated ships and travelers, a medieval tool against plague. Victorian sanitary reformers, who believed disease came from filth, often called it useless and costly to trade. By the 1870s–90s Britain replaced blanket ship quarantine with inspection, isolation of the sick and cleaner ports, while international conferences from 1851 sought common rules.
When and how
Ragusa (now Dubrovnik), 1377; Paris, 1851, the first International Sanitary Conference; British port health system from the 1870s.
How sure are we?
Conference records and British port-health laws document the shift; historian Krista Maglen has traced this 'English system'.
Debates and open questions
Whether quarantine stops epidemics or only delays them was argued then and still is, as debates over COVID-19 travel bans showed.