Quarantine is the restriction of movement or isolation of persons who have been exposed to a contagious disease before it is known whether they will become ill (WHO, 2019). It involves physically separating well individuals from others for a period that may exceed their expected incubation time for the disease, while providing them with care and essential services. It can be applied at the individual or community level and can include limiting contact with people who have not been exposed to the disease, tracing contacts, and providing antiviral medications. It can also include a home quarantine order. It can be enforced by public health or law enforcement officials. The federal government has quarantine authority and can issue isolation or quarantine orders, while state and local authorities have their own quarantine powers that can be used alongside the federal power. It is possible to have both federal and local quarantine in place at the same time during a disease outbreak, though this can be difficult to manage.
The committee found that while there is limited evidence about when quarantine reduces transmission of a disease, most studies on the effects of quarantine focus on measuring adherence (not infection), and are based on models that use historical data from actual outbreaks rather than new simulations of the disease process (called modelling studies). More research into real-time modeling during an epidemic would be helpful to improve the quality of future modeling.
In addition to measuring adherence, it is important to understand the secondary outcomes of quarantine, including harms such as financial and psychological stress. Ensuring that people under quarantine have a clear understanding of the severity of the outbreak and their role in epidemic control, as well as receiving adequate information about the reasons for their quarantine from health and government authorities, will increase adherence, making stressful experiences easier to bear.