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Isolation and Quarantine

What are quarantine measures?
Today, CDC uses quarantine to refer to any situation in which a person or group of personsor a building, conveyance, cargo, or animalthought to have been exposed to a dangerous communicable disease agent is kept apart from others (quarantined) to prevent disease spread. People who have been exposed to a communicable disease may be asked to remain at home to prevent further spread of infection. This public health measure may be compared with snow days, when travel is temporarily restricted and minor inconveniences are tolerated. The concept may also be referred to as shelter in place or quarantine.

In contrast, the word isolation is used when a sick patient(s) is/are kept separate from others (isolated), usually within a health care facility or at home. Typically, the ill person will have his or her own room, and those who care for him or her will wear protective clothing and take other barrier nursing precautions depending on the level of personal protection defined by the pathogen of concern.

Quarantine and isolation may be undertaken voluntarily or compelled by public health authorities.

Why are quarantine measures implemented?
Stopping an outbreak of disease sometimes requires the use of the most rapid and effective public health tools available. One of those tools is quarantinerestricting the movement of people who may have been exposed to infection to prevent them from infecting others. When most members of a population lack immunity to a contagious disease, quarantine of exposed persons (along with isolation of sick persons) may be the best initial way to prevent uncontrolled spread, especially when combined with other health strategies.

What are the duration and scope of quarantine measures?
The duration of quarantine measures may vary widely, depending on their purpose and what is known about the incubation period of the infectious agent. Examples include:

• A few hours for assessment. Passengers on a plane reasonably believed to carry a person infected with a dangerous contagious disease might be delayed for a few hours while health authorities determine the threat. Alternatively, passengers may be asked to provide contact information and then released, while the ill person is transported for medical attention.
• Enough time to provide prophylactic treatment or other intervention. If public health authorities determine a plane passenger is sick with a dangerous contagious disease, the other passengers may be quarantined in a designated facility where they may receive prophylactic treatment and be monitored for signs of side effects or illness.
• For the duration of the incubation period. If public health officials determine that a plane passenger is infected with has a contagious disease, and the passengers sitting close to him may have had close contact with the infected passenger, these passengers might be quarantined in a designated facility where they can be monitored for signs of illness and cared for under isolation conditions if they become ill.

Who has authority to implement quarantine?
States generally have authority to invoke and enforce quarantine within their jurisdictions. This authority derives from the states police power: the inherent authority of governments to enact laws and promote regulations to safeguard the health and welfare of its citizens. Other public health actions that can be compelled by state health authorities include school immunization and tuberculosis treatment laws.

Federal Quarantine authority, CDCs authority to implement quarantine measures, is derived from Section 361 of the Public Health Service Act (42 U.S.C. 264), as amended.

Have quarantine measures been implemented recently? If so, when?
Health officials in Singapore, Hong Kong, and Ontario have implemented population-based quarantine and isolation measures to limit the spread of SARS. In the United States in modern times, most quarantine measures have been imposed on a small scale, typically involving small numbers of travelers (airline or cruise ship passengers) who have curable diseases such as infectious tuberculosis or cholera. In fact, no instances of large-scale quarantine have occurred in the United States since the Spanish Flu pandemic of 191819.

For more information, visit http://www.cdc.gov/ncidod/sars/ or call the CDC public response hotline at (888) 246-2675 (English), (888) 246-2857 (Espaol), or (866) 874-2646 (TTY).

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This page last updated April 2, 2003
URL: http://www.cdc.gov/media/pressrel/r030402.htm

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