Optimal COVID-19 Quarantine and Testing Strategies
Speaker: Jeffrey Townsend, Yale University
Abstract: As the economic woes of the COVID-19 pandemic deepen, strategies are being formulated to avoid the need for prolonged stay-at-home orders while implementing risk-based quarantine, testing, contact tracing, and surveillance protocols. Given limited resources and the significant economic, public health, and operational challenges of the current 14-day quarantine recommendation, it is vital to understand if more efficient but equally effective quarantine and testing strategies can be deployed. To this end, we developed a mathematical model to quantify the probability of post-quarantine transmission that varied across a range of possible quarantine durations, timings of molecular testing, and estimated incubation periods. We found that a 13-day quarantine with testing on entry, a nine-day quarantine with testing on exit, and an eight-day quarantine with testing on both entry and exit each provide an equivalent or lower probability of post-quarantine transmission compared to a 14-day quarantine with no testing. We found that testing on exit from quarantine is more effective in reducing the probability of post-quarantine transmission than testing upon entry. When conducting a single test, testing on exit was most effective for quarantines of six days or shorter, while testing on day six or seven is optimal for longer quarantines. Optimal timing of testing during quarantine will reduce the probability of post-quarantine transmission, as false-positive results become less likely, enabling case isolation. Based on 4,040 SARS CoV-2 RT-PCR tests, an exit test 96 hours after the start of quarantine for an offshore oil rig population was demonstrated to identify all known asymptomatic cases that previously tested negative at entry, and—moreover—successfully prevented an expected seven or more offshore transmission events, each a serious concern for initiating rapid spread and a disabling outbreak in the close quarters of an offshore rig. This successful outcome highlights the importance of context-specific guidelines for the duration of quarantine and timing of testing that can minimize economic impacts, disruptions to operational integrity, and COVID-related public health risks.
Bio: Professor Townsend earned his Ph.D. in organismic and evolutionary biology from Harvard University in 2002, under Daniel Hartl. His Ph.D. research using S. cerevisiae was the first population genetic analysis of genome-wide gene expression variation. He then became a Miller Fellow at UC Berkeley, working on functional genomics with Neurospora crassa. Townsend's academic career began as an Assistant Professor at the University of Connecticut in 2004 and continued at Yale University in 2006. By 2013, he was an Associate Professor focusing on statistical models of disease spread and cancer evolution. He was named Elihu Professor in 2017 and was appointed a member of the Connecticut Academy of Science and Engineering in 2019 for his innovative population biology research. In 2021, he became Co-Chair-Elect of the Cancer Evolution Working Group of the American Association for Cancer Research and was appointed Co-Director of Yale Cancer Center's Genetics, Genomics, and Epigenetics Program in 2022. In 2023, he was elevated to Co-Chair of the Cancer Evolution Working Group.