Quarantine
The period of isolation decreed to control the spread of infectious disease.
Before the era of antibiotics, quarantine was one of the few available means for halting the spread of infectious diseases.
It is still employed as needed.
The list of quarantinable diseases in the US includes cholera, diphtheria, infectious tuberculosis, plague, smallpox, yellow fever, and viral hemorrhagic fevers (such as Marburg, Ebola and Congo-Crimean disease).
In 2003, SARS (severe acute respiratory syndrome) was added as a quarantinable disease.
The word 'quarantine' comes from the Latin word 'quadraginta' meaning forty.
This was probably because it was known that the incubation period of most infectious diseases was less than 40 days.
In 1348 Venice was the first city to impose a quarantine.