Reconstruction of SARS-CoV-2 outbreaks in a primary school using epidemiological and genomic data

Mathematical modeling studies have shown that repetitive screening can be used to mitigate SARS-CoV-2 transmission in primary schools while keeping schools open. However, not much is known about how transmission progresses within schools and whether there is a risk of importation to households. In this study, we reconstructed outbreaks observed during a prospective study in a primary school and associated households in Liege (Belgium) during the academic year 2020-2021. In addition we performed a simulation study to investigate how the accuracy of estimated weekly positivity rates in a school depends on the proportion of a school that is sampled in a repetitive screening strategy. We found that transmission occurred mainly within the school environment and that observed positivity rates are a good approximation to the true positivity rate, especially in children. This study shows that it is worthwile to implement repetitive testing in school settings, which in addition to reducing infections can lead to a better understanding of the extent of transmission in schools during a pandemic and importation risk at the community level.

Assessing the feasibility and effectiveness of household-pooled universal testing to control COVID-19 epidemics

Current outbreaks of SARS-CoV-2 are threatening the health care systems of several countries around the world. The control of SARS-CoV-2 epidemics currently relies on non-pharmaceutical interventions, such as social distancing, teleworking, mouth masks and contact tracing. However, as pre-symptomatic transmission remains an important driver of the epidemic, contact tracing efforts struggle to fully control SARS-CoV-2 epidemics. Therefore, in this work, we investigate to what extent the use of universal testing, i.e., an approach in which we screen the entire population, can be utilized to mitigate this epidemic. To this end, we rely on PCR test pooling of individuals that belong to the same households, to allow for a universal testing procedure that is feasible with the current testing capacity. We evaluate two isolation strategies: on the one hand pool isolation, where we isolate all individuals that belong to a positive PCR test pool, and on the other hand individual isolation, where we determine which of the individuals that belong to the positive PCR pool are positive, through an additional testing step. We evaluate this universal testing approach in the STRIDE individual-based epidemiological model in the context of the Belgian COVID-19 epidemic. As the organisation of universal testing will be challenging, we discuss the different aspects related to sample extraction and PCR testing, to demonstrate the feasibility of universal testing when a decentralized testing approach is used. We show through simulation, that weekly universal testing is able to control the epidemic, even when many of the contact reductions are relieved. Finally, our model shows that the use of universal testing in combination with stringent contact reductions could be considered as a strategy to eradicate the virus.

A prospect on the use of antiviral drugs to control local outbreaks of COVID-19

ObjectiveInvestigate the impact of using antiviral drugs to control local outbreaks of COVID-19. MethodsUsing a simulation-based model of viral transmission we tested the impact of different intervention measures for the control of COVID-19. ResultsThe use of an antiviral drug, in combination with contact tracing, quarantine and isolation, results in a significant decrease of the mean final size and the peak incidence of local outbreaks of COVID-19, provided delays in contact tracing are small. ConclusionsIntegrating antiviral drugs together with contact tracing and quarantine is predicted through this model to be an effective tool for the control of local outbreaks of COVID-19.