Protective sequestration

Protective sequestration is a public health term that refers to measures taken to protect a small, defined, and still-healthy population from an epidemic (or pandemic) "before" the infection reaches that population.

Given the extraordinary nature of these measures, they should be considered, if at all, only under exceptional circumstances: (1) implementation is feasible, (2) the measures can be enforced, and voluntary compliance of the sequestered population is highly likely, and (3) the sequestered population and/or the work they perform merits this effort and justifies the use of these measures. The term “protective sequestration” was coined by Drs. Markel and DiGiovanni, and colleagues, in their paper that described the successes and failures of several communities in the United States in their attempts to shield themselves from the 1918-1920 so-called “Spanish Influenza” pandemic during the second wave of that pandemic (September-December 1918). See Howard Markel, Alexandra M. Stern, J. Alexander Navarro, Joseph R. Michalsen, Arnold S. Monto, and Cleto DiGiovanni, Jr.,“Nonpharmaceutical Influenza Mitigation Strategies, US Communities, 1918-1920 Pandemic,” "Emerging Infectious Diseases", vol. 12, no. 12 [December 2006] ; available at http://www.cdc.gov/ncidod/eid/vol12no12/06-0506.htm.

The term “protective sequestration” avoids the use of the word “quarantine,” which, in public health, refers to the voluntary or enforced detention of a person who, because of actual or possible contact with a person carrying an infectious agent, may have acquired that agent and be capable of passing it along to others. The duration of the quarantine period is determined by the incubation period of the infection, i.e., the time between acquisition of the infectious agent and the development of signs or symptoms of the illness caused by that agent.

During the 1918-20 influenza pandemic, factors that contributed to the rare successes of protective sequestration were the following. First, the community leader(s) recognized the danger posed by the pandemic before it reached the community and implemented protective measures early (before neighboring communities did). Second, taking advantage of the community’s remoteness or natural barriers that were generally, but not always, present, the community leadership established and enforced a cordon around the outer perimeter of the community. Third, anyone seeking entry into the community was placed in quarantine for the incubation period of the infection and released into the community only after they were shown to be free of infection. Furthermore, the leadership established a system whereby supplies were delivered and received in a way that eliminated human-to-human contact with those delivering the supplies. Fourth, families were kept together so that life within the protected zone was as normal as possible. Schools remained in session and places of worship remained open, people continued to work, and entertainment remained available. Fifth, “protective sequestration” measures remained in effect for the duration of the risk.

An advantage of protective sequestration is that it shields selected people from infection and possibly buys them time for the development and distribution of drugs or vaccine. A disadvantage, apart from its elitism and social and economic cost, is that those sequestered have no opportunity to develop naturally-acquired immunity to the infectious agent through contact with it, and, therefore, they remain susceptible to the agent during subsequent waves of the epidemic or pandemic.