Isolation & Quarantine: How, When, and How Much

by Jerry Mothershead

Isolation and quarantine are topics of much recent debate among U.S. policymakers, emergency managers, and both public-health and medical-system officials. The recent State and Federal Public Health Preparedness Summit (22-24 February in Washington, D.C.) included several sessions dedicated to exploring these issues. The Summit was a follow-on to the January 2006 release of Issues to Consider: Isolation & Quarantine, a checklist developed by the National Association for City and County Health Officials.

Although both isolation and quarantine are important public-health working tools, emergency managers and other public officials involving in mitigating a public-health disaster must have a firm working knowledge of the risks, benefits, and challenges in using either of these tools. First, some basic definitions:

  • Isolation is a medical procedure, applied to an individual, a group of individuals, or potentially an entire population, who have a communicable (read “contagious”) disease, whereby the affected individual is separated from those not so affected for the duration of the time that the disease in question is communicable. It traditionally is applied in a hospital setting, but could be instituted in one’s home. Inherent in this definition are the following: Isolation is not applied to asymptomatic individuals; the isolated individual must be infected with a live, biological pathogen; and the person infected must be capable of transmitting the pathogen to others. Theoretically, all infectious diseases are communicable, but the ones of greatest concern are those transmitted through the air. 
  • Quarantine is the restriction, through voluntary or compulsory methods, of individuals who are without symptoms but are presumed to be infected with a biological pathogen capable of producing a communicable disease. The quarantine, a status established by a legally empowered authority, continues until those under quarantine no longer pose a transmission risk
  • “Shielding” – i.e., social distancing – includes those non-pharmacological actions taken to reduce an individual’s risk of exposure to a communicable disease or to reduce the probability of exposing someone else to the disease.

The Black Plague, SARS, and the U.S. Code

Isolation is a relatively new construct that has evolved in step with man’s knowledge of how diseases are transmitted. Quarantine has been around since at least Biblical times, and has sometimes been imposed incorrectly. During the Black Plague, a cordon sanitaire was instituted around some cities – reflecting the belief that transmission could occur only through infected humans – to keep those infected with the plague from coming in contact with other people.  

Quarantine has been used in the United States since colonial days, when it was imposed by city or colonial governments – primarily on arriving maritime traffic. Quarantine authorities are divided among federal, state, county, and local officials. In general, state and local public-health officials are responsible for quarantine issues within their states. 

Under a declared State of Emergency, though, governors have extraordinary powers to impose certain restrictions to protect the public.

Most recent uses of quarantine and isolation laws have targeted relatively small numbers of individuals, however. But experience in large-scale quarantine is rather skimpy, and many experts in this field have deemed state laws inadequate for dealing with large-scale public-health emergencies. For that and other reasons, many states have revised, or are in the processing of revising, their public-health laws, including those related to isolation and quarantine.

In doing so, some states have used the guidelines spelled out in the Model State Emergency Health Powers Act, which was developed in 2001 for the Centers for Disease Control and Prevention (CDC). Title 42 of the U.S. Code authorizes the U.S. Surgeon General to take any action needed, including the imposition of isolation and/or quarantine, to prevent the introduction from overseas, or through interstate spread, of certain communicable diseases (which must be identified as such by Executive Order).  In 2003, Executive Orders added several diseases, including Severe Acute Respiratory Syndrome (SARS), to the list.  Proposed (and sometimes controversial) revisions to 42 USC that will expand federal quarantine powers and empower certain non-governmental authorities already have been posted in the Federal Register.

States may assist the federal government, and vice versa, in implementing and enforcing isolation and quarantine. The use of this valuable containment tool in situations affecting a large number of people will therefore require both vertical coordination among several levels of government and horizontal collaboration across the nation’s public-health, public-safety, governmental-affairs, and law-enforcement communities.

Inequality Among Bugs

There are several fundamental issues that have yet to be addressed, however, and some important questions that have not yet been answered. Following are a few of the most important of those questions:   

1. Can quarantine and isolation work? Here the not totally satisfactory answer is “It depends.” Not all bugs are created equal. Each has specific characteristics that will influence the effectiveness of quarantine efforts.  Smallpox and influenza victims, for example, may transmit those diseases at the end of the disease incubation periods, but before the victims indicate signs of suffering from a major illness. In that situation, secondary victims will likely not even know they have been exposed prior to themselves becoming ill, thus allowing sufficient time for further spread.  In only one of the 20th-century influenza pandemics did quarantine have any effect, and that was in merely slowing disease progression.

On the other hand, the overall transmissibility of SARS is relatively low – which was a major factor in the apparent success of the quarantine and travel-advisory measures taken during the 2004-2005 outbreaks. Nonetheless, some level of quarantine may be mandatory to contain an epidemic more rapidly.  A CDC analysis focused on the containment of smallpox revealed that, without the institution of at least some limited quarantines, eradication in the United States of that disease might well take more than a year after even a relatively small outbreak.   

2. Can an effective quarantine strategy be devised?  Again, the answer is “It depends.” Quarantine could be instituted on a large scale to exclude a disease from the United States (scenario 1).  It also could be instituted to halt the interstate or inter-regional spread within the United States (scenario 2).  Considering the much discussed leakiness of the U.S. borders with Canada and Mexico, scenario 1 seems impossible.  

However, whole-nation quarantines were imposed in Australia, Madagascar, and elsewhere during the 1918-1919 Spanish Influenza Pandemic. Vigorous controlled quarantines on island nations appeared to be very effective, but in Australia only slowed, but did not stop, the spread of the disease. It should be remembered that the quarantine measures then instituted were well before widespread (and rapid) travel became the global norm. During the SARS epidemics, passenger screening was instituted in many locations, but because of the minimal size of the outbreaks it is difficult to ascertain the effectiveness of the measures taken. Proposed changes to 42 USC Sections 70 and 71 would empower the airline industry to “make the call” against individuals suspected of harboring a quarantinable disease. Many experts question the ability to train lay industry personnel to adequately make such decisions.  

Scenario 2 harkens images from the movie thriller “Outbreak,” but no one can doubt the extreme economic, emotional, and logistical support burdens that would arise from an attempt to quarantine even a small town or village in today’s United States. Road closures were attempted in Australia, Canada, and elsewhere during the 1918 pandemic, but were shown to have little effect, and many other countries rejected such measures outright as being unenforceable.

There may, however, be some utility in ordering a quarantine, even knowing it could not or would not be enforced. Slowing the progression of a pandemic would allow more time for the development, mass production, and distribution of medicines, and for taking various related medical countermeasures. Moreover, quarantines can be graduated, ranging from imposition on high-risk segments of society through the most draconian entire-population quarantine.

In any event, quarantine advisories are likely to be effective only to the degree that the public trusts the government. Targeted population quarantines may include the cancellation of mass-gathering events, or mass-transportation restrictions (imposed, for example, on bus, train, and airline travel). 

As the more extreme forms of compulsory quarantine (e.g., border closures and/or nighttime curfews) are instituted, compliance will be more difficult to ensure, enforcement will be problematic, and the logistical burden of maintaining critical-infrastructure operations will increase exponentially.  One very real option is to develop a cordon sanitaire approach to guarding many of these critical infrastructures – city reservoirs and nuclear power plants are among the more obvious examples – with volunteer skeleton crews sequestered at or close to those sites.    

3. Are there other quarantine-related actions that may be of value? Here the answer is a clear “Yes.” First among these actions should be a pre-outbreak public information and education program. Most citizens would be more inclined to follow instructions if those instructions make sense, are considered to be personally useful, and are presented in a non-alarming fashion by trusted sources. Unfortunately, there is abundant evidence that many citizens will not take the common-sense steps they should take before a catastrophe strikes. Hurricanes Katrina and Rita demonstrated the value, to individuals and to families, of personal-emergency action plans. But it cannot safely be assumed that the lessons learned from those catastrophes will be applied by large segments of the population prior to the onslaught of similar disasters in the future.

Preparing for the Super-Catastrophe

However, personal shielding and protective actions still may be of value. Simple common-sense actions such as the frequent washing of hands and, in times of disaster, the avoidance of highly crowded environments would greatly reduce (but not completely eliminate) the transmission of many diseases. The voluntary wearing of masks, although not proven to be totally effective, also may have value, if only to serve as a constant visible reminder to take other precautions.

Private businesses and corporations should review their own continuity plans as a corollary to whatever public actions are being taken. Telecommuting and outsourcing to the home environment should be made easier for as large a number of employees as possible. Even internally, the sequestration of company personnel into smaller cohorts of employees may help reduce the spread of disease – again, not eliminate, but reduce.

As part of this process, companies and public institutions should review their plans for “snow days” and consider using the same plans, modified as appropriate, in times of major emergencies. The greatest difference in using such plans to cope with disasters rather than for actual inclement-weather operations would be that the duration of the disaster probably would be significantly longer – and have a much greater impact on operations. That impact, however, could be mitigated to at least some extent through pre-planning.

To summarize: The imposition of quarantine as the primary solution to containing a highly contagious disease would probably not be practical. If history is any guide, it would not work with 100 percent effectiveness, compliance and enforcement would be extremely difficult, and the logistical problems that develop would be nearly impossible to overcome. A targeted quarantine, however – combined with personal shielding and/or other quarantine-like actions – might prove to be as effective in the long run.  Nonetheless, quarantine may serve as a valuable adjunctive containment measure to buy time – either to start other mitigation actions, or to maintain business and governmental continuity during a major public-health super-catastrophe.