The dark and complex history of quarantine goes back to the Middle Ages

During the 1918 influenza pandemic, warehouses like this one were converted to keep infected people quarantined.

(CNN)"Quarantine" is a word used for the precautionary isolation period that those possibly exposed to the novel coronavirus must face.

Thousands of people around the world are being quarantined as governments scramble to keep the virus from spreading. In China, thousands were forced into mass quarantine centers. In Italy, entire cities and towns were put on lockdown, effectively putting an estimated 100,000 under quarantine.
In the United States, quarantines are in place for some first responders who helped infected patients at a Seattle-area nursing home, or attendees of a New York bar mitzvah.
But while the spreading quarantines might feel unprecedented, this is not the first time they've been used to stop the spread of a deadly virus.
The word, and the practice, has a dark and complex history that goes back to the Middle Ages.

Bubonic plague in Venice (14th century)

The word "quarantine" itself is derived from the French word "quarantaine," which means "about 40," according to Merriam-Webster. The word was first used in English in 1617 to refer to the 40 days a ship suspected of carrying a contagious disease was held in isolation offshore.
But the first instance of the institutionalized practice of quarantine came much earlier, in the 14th century, according to the CDC.
The bubonic plague, or so-called Black Death, devastated Europe from 1347 to 1352, killing an estimated 20 million people.
When the plague started spreading in 1347 in Venice, Italy, ports started turning away ships suspected of coming from infected areas. By the following year, authorities in Venice became the first to formalize the protective action. They closed their ports to suspect ships and subjected travelers and legitimate ships to 40 days isolation, according to the Science Museum in London.

Congress takes quarantine into its own hands (1878)

As the United States developed in the 18th century, protection against contagious diseases fell under local and state jurisdictions, according to the Centers for Disease Control and Prevention.
After a 1793 yellow fever epidemic struck Philadelphia and killed 5,000, the city built a quarantine station called the Lazaretto along the Delaware River that occupied 10 acres, according to PBS.
But as outbreaks of yellow fever continued, Congress took action and passed the National Quarantine Act in 1878.
The legislation didn't conflict with states' rights, but paved the way for the federal government's involvement in quarantine activities.
Local quarantine stations were slowly turned over to the federal government and the quarantine system was fully nationalized by 1921, according to the CDC.

Court rules quarantine of Chinese was racist (1900)

In March 1900, Chick Gin, the Chinese owner of a lumberyard, died of bubonic plague in the Chinese quarter of San Francisco, according to PBS.
Authorities immediately cordoned off the 15-block neighborhood, quarantining about 25,000 Chinese residents and closing businesses owned by people who weren't white.
Later that year, a court ruled that the quarantine was racist and lifted it.
The judge declared that health officials acted with an "evil eye and an unequal hand," PBS said.

A bubonic plague epidemic (1901)

In Cape Town, South Africa, in 1901, an epide