Asymptomatic Transmission, the Achilles’ Heel of Current Strategies to Control Covid-19

Abstract

Traditional infection-control and public health strategies rely heavily on early detection of disease to contain spread. When Covid-19 burst onto the global scene, public health officials initially deployed interventions that were used to control severe acute respiratory syndrome (SARS) in 2003, including symptom-based case detection and subsequent testing to guide isolation and quarantine. This initial approach was justified by the many similarities between SARS-CoV-1 and SARS-CoV-2, including high genetic relatedness, transmission primarily through respiratory droplets, and the frequency of lower respiratory symptoms (fever, cough, and shortness of breath) with both infections developing a median of 5 days after exposure. However, despite the deployment of similar control interventions, the trajectories of the two epidemics have veered in dramatically different directions. Within 8 months, SARS was controlled after SARS-CoV-1 had infected approximately 8100 persons in limited geographic areas. Within 5 months, SARS-CoV-2 has infected more than 2.6 million people and continues to spread rapidly around the world.