Quarantine refers to the separation of people who have been exposed to a contagious pathogen before it is known whether they will become ill. This separation usually lasts longer than the incubation period of the disease, and is intended to prevent the spread of infection to other people who are not yet ill.
During times of epidemic, quarantine is typically implemented in a community, state or even country. It is often accompanied by other control measures such as travel restrictions and school closures, and can involve people at any level of exposure to the pathogen. As a result, it can have wide-ranging impacts on people, communities and economies.
Many of the questions raised by public health emergency preparedness and response (PHEPR) practitioners about quarantine concern how well it is implemented and how effective it is. Implementation challenges include deciding when to quarantine, who to quarantine, and how long to quarantine for. The effectiveness of quarantine also depends on the biology of the pathogen, including how quickly asymptomatic people become contagious and whether or when they start to show symptoms.
While there is a need to continue to measure metrics related to the impact of quarantine on the spread of infection, it is increasingly important to consider other outcomes that are associated with quarantine such as protection of civil rights and protection from avoidable harms. This requires a clear understanding of the population on which quarantine is imposed and a willingness to adapt rules and procedures accordingly.