These are terms that are often confused by the public. A quarantine involves restricting the moment of a healthy person who is suspected of exposure to a communicable disease, even if the person isn’t experiencing symptoms or doesn’t know if they have been exposed. The person is kept apart from the community during the time the pathogen is known to incubate and then become contagious to others.Isolation involves separating someone who is already sick and/or tested positive or a disease. The person is then kept apart from the community until they are no longer contagious. Quarantines and isolation may take place in the home, or other locations determined by health authorities.
Deeper dive
The history of quarantines goes back to the Middle Ages when the plague was sweeping through Europe. Venice, a major port, tried to stop the disease from entering its city by requiring ships suspected of harboring plague, to wait offshore for 40 days before people or goods could come ashore. The city also built a hospital off its coast, where sailors who came off ships with the plague were sent. The forty-day waiting period was called “quarantinario,” for the Italian word for forty. Hence the word “quarantine.”
Quarantines can be important when there is no vaccine or drug to treat a rapidly spreading disease, as was true in the early days of the COVID-19 pandemic. However, as the pandemic also demonstrated, quarantines are controversial because they involve separating healthy people from the community, and they raise civil liberties questions.
The Centers for Disease Control and Prevention, has the legal authority to quarantine and isolate a person at a U.S. airport, port or the border if the person is known to be infected or possibly infected with one of nine quarantinable diseases. The nine include: cholera, diphtheria, infectious tuberculosis, smallpox, yellow fever, viral hemorrhagic fevers, severe acute respiratory syndrome, new types of flu that could cause a pandemic, or a disease that has been designated by order of the President, as was done so with the COVID-19 pandemic.
During the first year of the COVID-19 pandemic, at the order of the president, the CDC restricted and banned international travel for non-U.S. citizens from some countries to slow the spread of the SARS-CoV-2 virus that causes COVID-19 disease.
The CDC also initially asked people to isolate in their homes for up to 10 days if they had symptoms or tested positive for COVID-19 and to quarantine for up to 10 days if they had been exposed, but changed its guidelines in August 2022. Those that test positive are asked to quarantine for 5 days. For those who have been exposed, but tested negative, the CDC no longer recommends quarantining, but rather encourages those exposed to wear a mask when in public and to test 5 days after exposure.