Patterns (Jun 2021)
An intra-host SARS-CoV-2 dynamics model to assess testing and quarantine strategies for incoming travelers, contact management, and de-isolation
Abstract
Summary: Non-pharmaceutical interventions (NPIs) remain decisive tools to contain SARS-CoV-2. Strategies that combine NPIs with testing may improve efficacy and shorten quarantine durations. We developed a stochastic within-host model of SARS-CoV-2 that captures temporal changes in test sensitivities, incubation periods, and infectious periods. We used the model to simulate relative transmission risk for (1) isolation of symptomatic individuals, (2) contact person management, and (3) quarantine of incoming travelers. We estimated that testing travelers at entry reduces transmission risks to 21.3% ([20.7, 23.9], by PCR) and 27.9% ([27.1, 31.1], by rapid diagnostic test [RDT]), compared with unrestricted entry. We calculated that 4 (PCR) or 5 (RDT) days of pre-test quarantine are non-inferior to 10 days of quarantine for incoming travelers and that 8 (PCR) or 10 (RDT) days of pre-test quarantine are non-inferior to 14 days of post-exposure quarantine. De-isolation of infected individuals 13 days after symptom onset may reduce the transmission risk to <0.2% (<0.01, 6.0). The bigger picture: In 2020, the COVID-19 outbreak turned into a pandemic. Non-pharmaceutical interventions (NPIs) remain decisive tools to prevent SARS-CoV-2 transmission and contain the spread of novel viral variants. Strategies that combine NPIs with SARS-CoV-2 testing may help to improve efficacy and shorten the duration of quarantine, thereby reducing the socioeconomic burden of SARS-CoV-2.We derived a novel intra-host viral dynamics model that realistically represents time-dependent infectiousness and test sensitivity profiles. We utilized this model to quantify the transmission risk reduction of combined NPI and testing strategies in different contexts. The underlying model is designed for rapid evaluation and flexibility in formulating NPI strategies and has been compiled into a user-friendly software (van der Toorn et al., 2021) that allows users to design and evaluate arbitrary NPIs schemes with regard to their efficacy in reducing the risk of SARS-CoV-2 onward transmission.
