Protective sequestration is a public health term that refers to social distancing measures taken to protect a small, defined, and still-healthy population from an epidemic (or pandemic) before the infection reaches that population. It is sometimes referred to as "reverse cordon sanitaire."

Given the extraordinary nature[clarification needed] of these measures, they should be considered, if at all, only under exceptional circumstances:

  • Implementation is feasible
  • The measures can be enforced, and voluntary compliance of the sequestered population is highly likely
  • 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 Howard Markel and his 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).[1]

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 flu pandemic, factors that contributed to the rare successes of protective sequestration were the following:

  • 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)
  • 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
  • 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
  • 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
  • Protective sequestration measures remained in effect for the duration of the risk.

The best known historical example is the measures taken by the town of Gunnison, Colorado during the 1918 influenza epidemic. To prevent an introduction of the infection, the town isolated itself from the surrounding area for two months at the end of 1918. All highways were barricaded near the county lines. Train conductors warned all passengers that if they stepped outside of the train in Gunnison, they would be arrested and quarantined for five days. As a result of the isolation, no one died of influenza in Gunnison during the epidemic.[2] Several other communities adopted similar measures.[1]

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.