Modeling the Comparative Impact of Individual Quarantine vs. Active Monitoring of Contacts for the Mitigation of COVID-19

Corey M Peak; Rebecca Kahn; Yonatan H Grad; Lauren M Childs; Ruoran Li; Marc Lipsitch; Caroline O Buckee

In December 2019, Coronavirus Disease (COVID-19) emerged in Wuhan, China. 1 It has since spread globally, reaching more than three dozen countries with over 80,000 confirmed cases by late February. 2 To reduce further spread of the disease, governments have implemented community measures to increase social distancing for those at highest risk of infection. 3 In China, policies include unprecedented lockdowns to reduce contacts between individuals, travel restrictions, and door-to-door temperature checks with mandatory mass quarantine. 4 Contact tracing, a core strategy to control disease, is used to identify individuals who may have been exposed to an infectious disease and to focus interventions on this high risk group. If identified contacts are symptomatic when found, they are promptly isolated and treated in a healthcare setting. More often, contacts are found healthy, and may or may not be infected. Depending on how much time has passed since exposure to the primary infected individual, those infected may not yet be symptomatic -this period of time between infection and symptoms is an important epidemiological trait of an infectious disease called the incubation period. How to handle these symptom-free contacts is a recurring point of confusion and controversy, particularly for emerging infectious diseases. Two essential strategies are used: individual quarantine and active monitoring. Individual quarantine involves the separation from others of an individual who is believed to be exposed to the disease, but not currently showing symptoms of it. A less restrictive intervention, active monitoring, involves assessing the individual for symptoms at regular intervals and, if symptoms are detected, promptly isolating the individual.