Quarantine helps restrict the actions and movements of people who may have a contagious disease to see if they get sick with it. Self-isolation involves physically separating people who have a contagious disease from those who do not.

The COVID-19 pandemic has triggered a state of emergency that allows federal, state, and local authorities to enforce measures such as lockdowns, quarantine, and self-isolation.

This article looks at the differences between quarantine and isolation and which diseases require them. It also looks at who sets and enforces rules to control the spread of contagious diseases in the United States.

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Quarantine helps prevent the spread of contagious diseases, such as COVID-19, by restricting close contact between people who are healthy and those who could transmit SARS-CoV-2, the virus that causes the disease.

Anyone who may have come into close contact with SARS-CoV-2 or someone with COVID-19 must quarantine. They will need to remain in quarantine or isolation until they know whether they have contracted the virus or not.

The Centers for Disease Control and Prevention (CDC) define close contact as:

  • providing care for someone with COVID-19
  • sharing drinking cups or eating utensils with someone with COVID-19
  • exposure to droplets from a sneeze, cough, or another source from someone with COVID-19
  • being within 6 feet of someone with COVID-19 for 15 minutes or more
  • hugging, kissing, or shaking hands with someone who has COVID-19

The CDC recommends people take the following steps to quarantine safely:

  • Stay at home for at least 14 successive days from the last point of contact with someone with COVID-19.
  • Stay away from others as best as possible, particularly people at a higher risk of developing severe illness.
  • Watch for symptoms, such as a fever of 100.4° F, shortness of breath, and other signs of COVID-19, and immediately self-isolate if they develop.
  • Wear a mask when around others, stay at least 6 feet away from other people, and avoid crowds.
  • Wash the hands frequently and thoroughly.
  • Tell others if a person thinks they may have been in contact with someone with COVID-19.

In some states, local health authorities may have specific rules on how long someone’s quarantine period should last. Some states offer options such as:

  • stopping quarantine 7 days after a negative test on day 5 or later after exposure
  • stopping quarantine 10 days after exposure without testing if no symptoms occur

Some people who have had exposure to SARS-CoV-2 may not need to quarantine, including people who:

  • are fully vaccinated and show no symptoms
  • have tested positive for COVID-19 within the past 3 months and are fully recovered or have no new symptoms

People with COVID-19 symptoms who can safely recover at home must self-isolate. People who test positive for COVID-19 but have no symptoms also need to self-isolate.

Self-isolation involves staying at home and keeping away from other people. The CDC recommends people take the following steps to self-isolate properly:

  • Stay at home except to seek medical care.
  • If people need medical care, call a local health authority or hotline first for advice.
  • Try to remain in one “sick” room or area and avoid sharing a washroom or kitchen with others, if possible.
  • Avoid contact with other household members and pets.
  • Wear a mask when around others.
  • Do not share personal items, such as towels, utensils, or cups.
  • Tell close contacts or local COVID-19 tracking apps about the situation.
  • Keep in touch with a doctor or healthcare professional.
  • Drink lots of fluids, rest, and use over-the-counter pain medications.
  • Clean and disinfect high-touch or shared surfaces frequently.

According to the CDC, people can come out of isolation and be around others again when they meet the following terms:

  • It has been at least 10 days since symptoms developed.
  • It has been 24 hours since experiencing a fever or using fever-reducing medications.
  • Other symptoms are improving, except for taste and smell changes, which may last for weeks to months and are not factors for self-isolating.

People who test positive for COVID-19 but do not experience symptoms may be able to stop self-isolating 10 days after their positive test. However, if any symptoms develop, they must begin self-isolation again.

People with weakened immune systems or those who experienced severe COVID-19 symptoms and hospitalization may need to self-isolate for up to 20 days.

Federal authority for isolation and quarantine comes from the Commerce Clause of the U.S. Constitution.

The U.S. Secretary of Health and Human Services has the authority to prevent the entry and spread of contagious diseases into the U.S. and between states.

The CDC is responsible for carrying out daily actions to limit contagious diseases. The 42 Code of Federal Regulations gives the CDC authority to:

  • detain, medically examine, and release persons entering the U.S. or traveling between states who may be carrying a contagious disease
  • regularly monitor persons entering U.S. land border crossings and other ports of entry for symptoms and signs of disease

A pilot or captain of a ship can also report passengers or crew members that may be sick to the CDC before they arrive.

If the CDC believes someone has a contagious disease, they have the right to detain them as necessary to investigate the cause of illness.

U.S. Customers and Border Protection officers and U.S. Coast Guard officers also have the authority to enforce federal quarantine orders.

The CDC maintains a “Do Not Board” list to prevent people who have or may have contracted a contagious disease from boarding commercial airplanes.

The CDC also maintains a “Lookout” list of people with sickness who may be traveling to prevent them from entering the U.S. by sea or land crossings.

A person may be on the list if:

  • they have acquired a serious, contagious disease
  • they are not aware of their diagnosis status yet or not following public health rules
  • they are likely to try to travel
  • there is a need to reduce travel in response to a public health outbreak

Authorization for federally enforced quarantine and isolation includes the following diseases:

States can use police power to enforce federal isolation or quarantine orders.

Laws vary between states. Some states have very specific laws, while the laws in other states are much broader.

Some states allow health authorities to carry out state laws. In most states, quarantine or isolation violations are a criminal offence. People who break federal quarantine orders may face fines and imprisonment.

According to the CDC, tribal police also have the authority to perform actions to protect the safety, health, and welfare of their tribal members.

In some cases, enforcement of state, local, tribal, and federal authority may happen at the same time. If there is a dispute between laws, federal laws always take precedent.

Quarantine and isolation both reduce the spread of contagious diseases.

Quarantine restricts the movement of people who have had exposure to a contagious disease to see if they develop the illness.

Isolation separates someone who has contracted a contagious disease from others.

People exposed to someone with COVID-19 or infected respiratory droplets should practice quarantine for 14 days.

People who have COVID-19 should self-isolate for at least 10 days after symptoms develop. After this time, they may break isolation if they have been fever-free for at least 24 hours and other symptoms are improving.