Isolation and quarantine are two strategies that can be used to control the spread of a disease that is contagious. Both approaches minimize the exposure of other people to infected persons.

Isolation and quarantine are not the same. Isolation is more common than quarantine and is used for someone who is known to have a disease. Quarantine is used for someone who has been exposed to a disease or disease-causing agent but who is not currently displaying symptoms and who may not necessarily become ill.

Isolation and quarantine may be voluntary. During a voluntary quarantine, people may elect to remain at home, forgo public gatherings, and curtail travel on airplanes, buses, trains, and other forms of public transit. However, if an outbreak involves a disease that is judged by public health authorities to be a severe contagious threat, isolation or quarantine may be imposed bylaw. In the United States only disease threats that are listed in an executive order by the president qualify for government-imposed quarantine.

The concept of quarantine dates back to the 14th century, when ships arriving in Venice, Italy, from regions where plague was occurring were required to anchor in the harbor for 40 days before the crew was permitted to go ashore. The word quarantine is derived from the Italian quaranta giorni, meaning 40 days.

In the United States federal legislation governing the imposition of quarantine was first enacted in 1878 in response to outbreaks of yellow fever. Then the quarantine powers of the federal government were minimal and did not override state and local government public health practices. The federal government assumed more responsibility for quarantine in 1892 in response to cholera outbreaks.

While states continue to have powers to issue quarantines for illnesses within their borders, the federal government has been responsible for quarantine on a national scale since the implementation of the 1944 Public Health Service Act. In 1967 federal responsibility for the imposition and enforcement of quarantine was transferred to the US Centers for Disease Control and Prevention (CDC), where it has remained. The Division of Global Migration and Quarantine (DSMQ) is responsible for the nationwide system of quarantine stations. As of 2017 there were 20 stations located at various ports of entry to the United States.

Both quarantine and isolation are designed to protect the larger community from people known to be infected with a contagious disease deemed to be a public health threat (isolation) or people who have had contact with someone who has become ill with the disease and so who may themselves be infected while not yet displaying symptoms (quarantine). Those in isolation can be treated while at the same time minimizing the chance that the disease will spread. People under quarantine can be monitored for symptoms of the diseases. If symptoms do not appear Page 509  |  Top of Articlewithin a certain time (10 days is typical, as voluntary compliance with a quarantine becomes difficult after that), then the quarantine can be lifted.

Isolation and quarantine are public health responses to an illness outbreak. Isolation is more common and is practiced daily in most hospitals, particularly since the appearance and increasing prevalence of tuberculosis and disease-causing bacteria that are resistant to multiple antibiotics. Examples include methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and carbapenem-resistant Enterobacte-riaceae (CRE). Many hospitals post warnings restricting visitation to a ward room housing a patient with a contagious infection.

Quarantine can affect civil liberties. Imposed quarantines may restrict freedoms of movement and assembly. Schools, restaurants, businesses, means of transit, and public spaces may be closed. The degree to which civil liberties are curtailed in response to an epidemic may be controversial, and, whenever possible, quarantine is a voluntary measure. In the event of an imposed quarantine, government entities, law enforcement, media, and public health organizations should provide as much information as possible to those affected by a quarantine.

Newborn babies are sometimes held in quarantine for the first hours after their birth. This practice allows health care professionals to monitor their health and ensure that they have not been exposed to any infectious diseases. © Petri Oeschger/Getty Images © Petri Oeschger/Getty Images

Isolation and quarantine can also affect an individual's privacy, because out of necessity the community will need to know who is being contained. This lack of privacy can even include revealing a person's medical history. Thus, isolation and quarantine are considered carefully and not undertaken without a demonstrated and immediate need to do so.

In the United States an executive order of the president identifies quarantinable diseases and authorizes government action to implement quarantines, restrict travel, and detain persons to stop the spread of certain infectious diseases. Executive Order 13295 lists cholera, diphtheria, infectious tuberculosis, plague, smallpox, yellow fever, and viral hemorrhagic fevers (such as Ebola, Marburg, and others) as quarantinable. In 2003, following an outbreak in Asia, severe acute respiratory syndrome (SARS) was added to the list. The growing threat of H5N1 virus and possible pandemic influenza prompted the Department of Health and Human Services (HHS) to request its addition to the list. On July 31, 2014, US President Barack Obama amended Executive Order 13295, identifying severe acute respiratory syndromes as quarantinable in the United States.

Increased movement of peoples worldwide through migration, travel, or war has prompted the need for better international protocols for preventing the spread of infectious diseases. Quarantine across national borders is problematic, sometimes complicated by war, political tensions, different languages, differences in the delivery of health care or in managing outbreaks, and legal systems. In the late 20th and early 21st centuries, national governments Page 510  |  Top of Articleand international agencies have worked to develop a global network of disease reporting. Increased communication about outbreaks of infectious diseases help nations prepare for disease threats and enact preventive measures within their own borders. The World Health Organization (WHO) and other nongovernmental organizations (NGOs), such as Doctors Without Borders, also report and respond to infectious disease outbreaks. International agencies and NGOs typically work with national and local governments to implement disease treatment and prevention strategies, including recommendations of isolation or voluntary or imposed quarantine.

Isolation and quarantine is not an exact science. The latest example of this occurred in Texas in 2016. A nurse in a Texas hospital contracted an infection caused by the Ebola virus during the treatment of a patient who had come to the United States from Liberia—then a site of an ongoing Ebola outbreak in Africa. In a series of errors, the patient's condition was not recognized. Even after Ebola was identified and the patient began receiving treatment, a breach in the hospital's protocol for the handling of infectious diseases deemed especially dangerous exposed the nurse to the infection. The patient ultimately died. The nurse recovered and successfully sued the hospital, arguing that the hospital's policy did not adequately protect her. As of 2017 the hospital denied the claim of negligence.