What is a quarantine, and what is the difference between quarantine and isolation? The CDC has issued a fact sheet and a Q&A on the subject.
Modern quarantine is used when a person or a well-defined group of people has been exposed to a highly dangerous and highly contagious disease, resources are available to care for quarantined people, and resources are available to implement and maintain the quarantine and deliver essential services.
Modern quarantine includes a range of disease control strategies that may be used individually or in combination, including: short-term, voluntary home curfew, restrictions on the assembly of groups of people (for example, school events), cancellation of public events, the suspension of public gatherings and closings of public places (such as theaters), restrictions on travel (air, rail, water, motor vehicle, pedestrian), the closure of mass transit systems, restrictions on passage into and out of an area.
Modern quarantine is used in combination with other public health tools, such as: Enhanced disease surveillance and symptom monitoring, rapid diagnosis and treatment for those who fall ill, and preventive treatment for quarantined individuals including vaccination or prophylactic treatment for some diseases.
Modern quarantine is more likely to involve limited numbers of exposed persons in small areas than to involve large numbers of persons in whole neighborhoods or cities, according to the CDC. The small areas may be thought of as “rings” drawn around individual disease cases. The CDC cites examples of rings:
– People on an airplane or cruise ship on which a passenger is ill with a suspected contagious disease for which quarantine can serve to limit exposure to others.
– People in a stadium, theater or similar setting where an intentional release of a contagious disease has occurred.
– People who have contact with an infected person whose source of disease exposure is unknown—and therefore may be due to a covert release of a contagious disease.
When someone is known to be ill with a contagious disease, they are placed in isolation and receive special care, with precautions taken to protect uninfected people from exposure to the disease.
When someone has been exposed to a contagious disease and it is not yet known if they have caught it, they may be quarantined or separated from others who have not been exposed to the disease. For example, they may be asked to remain at home to prevent further potential spread of the illness. They also receive special care and observation for any early signs of the illness.
The list of diseases for which quarantine or isolation is authorized is specified in a presidential executive order. The list currently includes cholera, diphtheria, infectious tuberculosis, plague, smallpox, yellow fever, viral hemorrhagic fevers (Ebola, Lassa, Marburg, Crimean-Congo, South American), Severe Acute Respiratory Syndrome (SARS), and influenza caused by influenza viruses that are causing or have the potential to cause a pandemic.
Isolation lasts for the period of communicability of the illness, which varies by disease and the availability of specific treatment. Usually it occurs at a hospital or other health care facility or in the person’s 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 precautions, depending on the level of personal protection needed for the specific illness. In most cases, isolation is voluntary, but federal, state and local governments have the authority to require the isolation of sick people to protect the public.
Modern quarantine lasts only as long as necessary to protect the public by providing public health care and ensuring that quarantined persons do not infect others if they have been exposed to a contagious disease.
Quarantined individuals are sheltered, fed, and cared for at home, in a designated emergency facility, or in a specialized hospital, depending on the disease and the available resources. They will also be among the first to receive all available medical interventions to prevent and control disease, including: vaccination, antibiotics, early and rapid diagnostic testing and symptom monitoring, and early treatment if symptoms appear.
The duration and scope of quarantine varies depending on the purpose and what is known about how long it takes for symptoms to develop after exposure.
If people in a certain area are potentially exposed to a contagious disease, state and local health authorities let people know that they may have been exposed and direct them to get medical attention, undergo diagnostic tests, and stay at home, limiting their contact with people who have not been exposed to the disease. Only rarely do federal, state, or local health authorities issue a manadatory order for quarantine and isolation. Quarantine and isolation may be compelled on a mandatory basis through legal authority, as well as conducted on a voluntary basis.
States have the authority to declare and enforce quarantine and isolation within their borders. This authority varies widely, depending on state laws. The CDC may detain, medically examine or conditionally release persons suspected of having certain contagious diseases. This authority applies to individuals arriving from foreign countries, including Canada and Mexico, on airplanes, trains, automobiles, boats or by foot. It also applies to individuals traveling from one state to another or in the event of “inadequate local control.”
The CDC regularly uses its authority to monitor passengers arriving in the United States for contagious diseases. 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. No instances of large-scale quarantine have occurred in the U.S. since the “Spanish Flu” pandemic of 1918-1919.
According to the CDC, the need to use its federal authority to involuntarily quarantine a person occurs only in rare situations—for example, if a person posed a threat to public health and refused to cooperate with a voluntary request.