In the event of a biological attack or the introduction of a highly contagious disease affecting the public, the U.S. health system may take measures to prevent those people infected with or exposed to a disease or a disease-causing biological agent from infecting others. The terms used to describe these measures, quarantine and isolation , generally apply to distinct groups of persons but are often used interchangeably. Quarantine typically refers to the "(s)eparation of individuals who have been exposed to an infection but are not yet ill from others who have not been exposed to the transmissible infection." In contrast, isolation refers to the "(s)eparation of infected individuals from those who are not infected." Varying degrees of quarantine exist, and the authority to order quarantine or isolation is generally very broad. Primary quarantine authority typically resides with state health departments and health officials; however, the federal government has jurisdiction over interstate and foreign quarantine. In addition, the federal government may assist with or take over the management of an intrastate incident if requested by a state or if the federal government determines local efforts are inadequate. The variety of potential responses—from federal, state, and local authorities—implicates a number of legal issues. Namely, who is responsible for preventing an outbreak of the disease; and precisely what may be done? This report will examine federal and state authority to impose quarantine and isolation measures in order to prevent the spread of infectious disease. Federal quarantine and isolation authority derives from the Commerce Clause of the U.S. Constitution, which states that Congress shall have the power "[t]o regulate Commerce with foreign Nations, and among the several states." Section 361 of the Public Health Service Act (PHS Act) grants the Secretary of Health and Human Services (Secretary) the authority to make and enforce regulations necessary "to prevent the introduction, transmission, or spread of communicable diseases from foreign countries into the States or possessions, or from one State or possession into any other State or possession." The law provides the Secretary with broad authority to apprehend, detain, or conditionally release a person. However, the Secretary may only exercise this authority in relation to communicable diseases published in an executive order issued by the President. Executive Order 13295 lists the communicable diseases for which this quarantine authority may be exercised. In 2000, the Secretary transferred certain authorities related to persons, including quarantine authority, to the Director of the CDC. Both interstate and foreign quarantine measures are now carried out by CDC's Division of Global Migration and Quarantine. Generally, federal regulations authorizing the apprehension, detention, examination, or conditional release of individuals are applicable only to individuals coming into a state or possession from a foreign country or possession. To facilitate containment efforts, federal regulations require airline pilots and ship captains to report immediately the presence of ill passengers on board their vessels. In addition, Section 361 of the PHS Act authorizes the apprehension and examination of any individual reasonably believed to be infected with a communicable disease in a qualifying stage and (A) to be moving or about to move from a State to another State; or (B) to be a probable source of infection to individuals who, while infected with such disease in a qualifying stage, will be moving from a State to another State. If found to be infected, such individuals may be detained for such time and in such manner as may be reasonably necessary. During times of war, the authority to apprehend and examine individuals extends to any individual "reasonably believed (1) to be infected with such disease [as specified in an Executive order of the President] and (2) to be a probable source of infection to members of the armed forces of the United States or to individuals engaged in the production or transportation of ... supplies for the armed forces." Regulations promulgated pursuant to this authority under the PHS Act may be found in Parts 70 and 71 of Title 42 of the Code of Federal Regulations. Part 70 applies to interstate travel, Part 71 to foreign arrivals. The implementing regulations authorize the quarantine and isolation of individuals in order to prevent the spread of diseases identified in Executive Order 13295. In addition, pilots of both interstate flights and flights to the United States are required to report certain illnesses they encounter during flight in advance of their arrival into the United States to the CDC Quarantine Station closest to their destination airport. There are currently 20 such stations operated by the CDC located at ports of entry into the United States. While there are not CDC officials at every port of entry, various agencies in the Department of Homeland Security (DHS) are authorized to assist the CDC in "the enforcement of quarantine rules and regulations." The Director of the CDC is also authorized to take measures as may be necessary to prevent the spread of a communicable disease from one state or possession to any other state or possession if he determines that measures taken by local health authorities are inadequate to prevent the spread of the disease. To prevent the spread of diseases between states, the regulations prohibit infected persons from traveling from one state to another without a permit from the health officer of the state, possession, or locality of destination, if such a permit is required under the law applicable to the place of destination. Additional requirements apply to persons who are in the "communicable period of cholera, plague, smallpox, typhus or yellow fever, or who having been exposed to any such disease, is in the incubation period thereof." The Secretary is also authorized to bar the entry of persons from foreign countries where the "existence of any communicable disease" poses a "serious danger" of entering the United States such that "a suspension of the right to introduce such persons and property is required in the interest of public health." A rule implementing this statutory authority was proposed in 2005, but was not adopted. The PHS Act and related statutes also authorize measures to aid or enforce a quarantine in the event of a public health emergency. Section 322(a) of the PHS Act authorizes the PHS to care for and treat persons under quarantine. Such persons may also receive care and treatment at the expense of the PHS from public or private medical facilities when authorized by the officer in charge of the PHS station at which the application is made. Section 311 of the PHS Act provides for federal-state cooperative activities to enforce quarantines. The federal government may assist states and localities in enforcing their quarantines and other health regulations and, in turn, may accept state and local assistance in enforcing federal quarantines. Under the authority of 42 U.S.C. § 97, the Secretary may request the aid of CBP, the Coast Guard, and military officers in the execution of quarantines imposed by states on vessels coming into ports. Criminal sanctions are prescribed for violations of federal regulations issued pursuant to Section 361 of the PHS Act. Violation of a federal quarantine or isolation order is a criminal misdemeanor, and individuals may be subject to a fine of up to $100,000, one year in jail, or both; organizational violations may be subject to fines of up to $200,000 per event. Federal district courts may enjoin individuals and organizations from violation of CDC quarantine regulations. In recent years, federal agencies have developed a travel restriction tool to prevent the spread of communicable diseases of public health significance. The public health Do Not Board (DNB) list was developed by DHS and the CDC, and made operational in June 2007. The DNB list enables domestic and international health officials to request that persons with communicable diseases who meet specific criteria and pose a serious threat to the public be restricted from boarding commercial aircraft departing from or arriving in the United States. The list provides a tool for management of emerging public health threats when local public health efforts are not sufficient to keep certain contagious individuals from boarding commercial flights. In order to place a person on the DNB list, state and local health officials contact their local CDC quarantine station. The CDC determines if the person is (1) likely contagious with a communicable disease that presents a serious public health threat, (2) unaware of or likely not to comply with public health recommendations and medical treatment, and (3) likely to try boarding a commercial aircraft. Once a person is placed on the DNB list, airlines are instructed not to issue a boarding pass to the person for any commercial domestic flight or for a commercial international flight arriving in or departing from the United States. Other forms of transportation, such as buses and trains, are not covered by the DNB list. Once a patient is determined to be noncontagious, the CDC and DHS must remove the person from the list, usually within 24 hours. In September 2008, the CDC released a report in which it analyzed the first year's experience with the DNB list. According to the report, the CDC received 42 requests to add persons to the DNB list, all of whom had suspected or confirmed pulmonary tuberculosis. The agency approved 33 of the requests, of which 28 were placed by public health departments in the United States, and 14 were placed on the list while they were outside of the country. Two of the 33 persons placed on the DNB list attempted to evade the air travel restriction, and both were detained by border officials and taken to local hospitals for evaluation and treatment. The CDC found that "[j]udicious use of the public health DNB list can obviate the human and economic costs associated with conducting contact investigations when people with communicable diseases travel on commercial aircraft." While the federal government has authority to authorize quarantine and isolation under certain circumstances, the primary authority for quarantine and isolation exists at the state level as an exercise of the state's police power. CDC acknowledges this deference to state authority as follows: In general, CDC defers to the state and local health authorities in their primary use of their own separate quarantine powers. Based upon long experience and collaborative working relationships with our state and local partners, CDC continues to anticipate the need to use this federal authority to quarantine an exposed person only in rare situations, such as events at ports of entry or in similar time-sensitive settings. Although every state has the authority to pass and enforce quarantine laws as an exercise of its police powers, these laws vary widely by state. Generally, state and local quarantines are authorized through public health orders, though some states may require a court order before an individual is detained. For example, in Louisiana, the state health officer is not authorized to "confine [a person] in any institution unless directed or authorized to do so by the judge of the parish in which the person is located." Diseases subject to quarantine may be defined by statute, with some statutes addressing only a single disease, or the state health department may be granted the authority to decide which diseases are communicable and therefore subject to quarantine. States also employ different methods for determining the duration of the quarantine or isolation period. Generally, "release is accomplished when a determination is made that the person is no longer a threat to the public health, or no longer infectious." One common characteristic of many state quarantine laws is their "overall antiquity," with many statutes being between 40 and 100 years old. The more antiquated laws "often do not reflect contemporary scientific understandings of disease, [or] current treatments of choice." In the past, state laws were often enacted with a focus on a particular disease, such as tuberculosis or typhoid fever, leading to inconsistent approaches in addressing other diseases. Until recently, despite the inconsistencies and perceived problems with such laws, state legislatures have not been forced to reevaluate their quarantine and isolation laws due to a decline in infectious diseases and advances in public health and medicine. However, in light of recent threats and security concerns, many states have begun to reconsider their emergency response systems, including the state's authority to quarantine. A review of quarantine authority was listed as a priority for state governments in the President's 2002 National Strategy for Homeland Security. Federal authority over interstate and foreign travel is clearly delineated under constitutional and statutory provisions. Less clear, however, is whether the state police powers may be used to restrict interstate travel to prevent the spread of disease. In a public health emergency, federal, state, and local authorities may overlap. For example, both federal and state agencies may have quarantine authority over an aircraft arriving in a large city from a foreign country. Thus, coordination between the various levels of government would be essential during a widespread public health emergency. Public health measures in emergency situations, including quarantine, involve balancing the rights of individuals with the state's police power to protect the needs of the public health, safety, and general welfare. Historically, this balance can be seen in public health crises over the past century or so. The U.S. Constitution and federal civil rights laws provide for individual due process and equal protection rights as well as a right to privacy, but these rights are balanced against the needs of the community. However, classic public health measures such as quarantine, isolation, and contact tracing are, nevertheless, available in appropriate situations, and, as new or resurgent diseases have become less treatable, some of these classic public health measures have been increasingly used. Therefore, the issue of how to balance these various interests in a modern culture that is sensitive to issues of individual rights has become critical. Some courts have recognized an individual's right to challenge his or her quarantine or isolation by petitioning for a writ of habeas corpus. Although the primary function of a writ of habeas corpus is to test the legality of the detention, petitioners often seek a declaration that the statute under which they were quarantined is unconstitutional. In 1824, the Supreme Court in Gibbons v. Ogden alluded to a state's authority to quarantine under the police powers. In 1902, the Court directly addressed a state's power to quarantine an entire geographic area in Compagnie Francaise de Navigation a Vapeur v. Louisiana State Board of Health , where both the law and its implementation were upheld as valid exercises of the state's police power. A shipping company in this case challenged an interpretation of a state statute that conferred upon the state board of health the authority to exclude healthy persons, whether they came from without or within the state, from a geographic area infested with a disease. The shipping company alleged that the statute as interpreted interfered with interstate commerce, and thus was an unconstitutional violation of the Commerce Clause. The Court rejected this argument, holding that although the statute may have had an effect on commerce, it was not unconstitutional. In a subsequent case, the Court made clear that at least where Congress has not taken action, it is "well settled" that states may impose quarantines to prevent the spread of disease even though quarantines "affect interstate commerce." In general, courts appear to have declined to interfere with a state's exercise of police powers with regard to public health matters "except where the regulations adopted for the protection of the public health are arbitrary, oppressive and unreasonable." For example, in Miller v. Campbell City , an order to evacuate an area was issued due to leaking methane and hydrogen gases. After some residents from a subdivision in the area became ill, the county commissioners declared the subdivision uninhabitable. The plaintiff was arrested when he crossed the roadblock enforcing the quarantine in an attempt to return home. The Tenth Circuit Court of Appeals upheld a finding that the evacuation order was substantially related to the public health and safety, and found no evidence that the quarantine action was taken in bad faith or maliciously. The court noted that the county needed to act quickly because of the potential danger, and did so "with appropriate concern for the situation and the interests of all involved." The court therefore found that the plaintiffs were not denied substantive due process. The court also held that because the plaintiffs were given the opportunity to present their objections orally to the local authorities, and could have entered written materials as well, the protections of procedural due process were satisfied. Similarly, a federal district court in United States v. Shinnick upheld the PHS's medical isolation of an arriving passenger because she had been in Stockholm, Sweden, a city declared by the World Health Organization to be a smallpox-infected area, and she could not show proof of vaccination. Likewise, a state court in People ex rel. Barmore v. Robertson refused to grant a habeas corpus petition for a woman who ran a boarding house where a person infected with typhoid fever had boarded. The woman was not herself infected with the disease, but she was a carrier and had been quarantined in her home. She argued that her quarantine was unwarranted because she was not "actually sick," though the court noted that "[i]t is not necessary that one be actually sick, as that term is usually applied, in order that the health authorities have the right to restrain his liberties by quarantine regulations." In justifying quarantine under these circumstances, the court explained that because disease germs are carried by human beings, and as the purpose of an effective quarantine is to prevent the spread of the disease to those who are not infected, anyone who carries the germs must be quarantined. The court found that in the case of a person infected with typhoid fever, anyone who had come into contact with that person must be quarantined to prevent the spread of the disease. More recently, a federal district court in New York dismissed a claim alleging violation of substantive and procedural due process by a plaintiff who was diagnosed with tuberculosis and confined to a hospital for a few days against his will. The court cited to Justice Burger's concurrence in O'Connor v. Donaldson , which noted that, pursuant to its police powers, a "[s]tate may confine individuals solely to protect society from the dangers of significant antisocial acts or communicable disease." However, at least one state court has ruled that when a state confines an individual in order to prevent the spread of disease, the state must provide the individual with procedural due process protections such as, inter alia , notice explaining the grounds for confinement, the right to counsel, and the right to engage in cross-examination. However, some courts have refused to uphold the quarantine of an individual in cases where the state is unable to meet its burden of proof concerning that individual's potential danger to others, or if a restriction is viewed as unreasonable or oppressive. In Wong Wai v. Williamson , the San Francisco Board of Health ordered all Chinese residents to be inoculated against bubonic plague and restricted their right to leave the city, citing nine deaths allegedly from plague. The inoculations were tainted, causing severe consequences. A court inferred that the regulations were properly authorized, but nevertheless struck them down as "not based on any established distinction in the conditions that are supposed to attend the plague, or the persons exposed to its contagions." Shortly after, in Jew Ho v. Williamson , the same court noted that the quarantine requirements applied only to Chinese residents and questioned whether bubonic plague actually caused the reported deaths. It invalidated the quarantine because it was "unreasonable, unjust and oppressive" and constituted discrimination in violation of the Fourteenth Amendment. Additional legal issues might be raised if quarantine, isolation, and other public health measures were used to deal with a widespread domestic public health emergency. If government agencies requisition private facilities for quarantine purposes, such as in the case of overburdened medical facilities, the legal questions regarding eminent domain power may arise. A new development in the law relating to quarantine is the possible use of self-imposed or home quarantines. States may need to consider whether their ability to impose quarantine also includes the authorities necessary to support a population asked to voluntarily stay at home for a period of time. Such authority may include the ability to offer legal immunity to businesses asked to provide facilities for quarantine. 

Summary: In the wake of increasing fears about the spread of highly contagious diseases, federal, state, and local governments have become increasingly aware of the need for a comprehensive public health response to such events. An effective response could include the quarantine of persons exposed to infectious biological agents that are naturally occurring or released during a terrorist attack, the isolation of infected persons, and the quarantine of certain cities or neighborhoods. The public health authority of the states derives from the police powers granted by their constitutions and reserved to them by the Tenth Amendment to the U.S. Constitution. The authority of the federal government to prescribe quarantine and other health measures is based on the Commerce Clause, which gives Congress exclusive authority to regulate interstate and foreign commerce. Thus, state and local governments have the primary authority to control the spread of dangerous diseases within their jurisdictions, and the federal government has authority to quarantine and impose other health measures to prevent the spread of diseases from foreign countries and between states. In addition, the federal government may assist state efforts to prevent the spread of communicable diseases if requested by a state or if state efforts are inadequate to halt the spread of disease. This report provides an overview of federal and state public health laws as they relate to the quarantine and isolation of individuals and a discussion of constitutional issues that may be raised should individual liberties be restricted in a quarantine or isolation situation.