ABSTRACT
Introduction: As new strains of SARCOV2 virus emerge across the world, it is imperative to investigate measures which restrict the movement of the general population such as social and travel restrictions by lockdowns to mitigate the effects of COVID-19. Thus, our paper helps in two ways: 1) Drastic measures like lockdown are essential but cannot be a feasible long-term intervention. Therefore, it is crucial to understand if the same unlock down can be reversed without compromising public health needs. Our paper provides evidence on the same;and 2) Our report also provides an insight into the trends of disease transmission during different phases of the un-lockdown. Methods: We examine the spread of pandemic during different phases of Un-lockdown (8th June to 31st October 2020). Since Rt calculation takes into consideration numerous factors, we use β, the transmission coefficient that governs the transition of population from Susceptible to Exposed pool, to examine the effect of public heaThelth interventions on disease spread. Results: The comparison of the distribution of fitted β values, thus calculated using SEIR model and GLM have been done and a Welch Two Sample t-test suggests that the GLM fitted β and SEIR β data sets are not significantly different from one another. Conclusion: We provide evidence that un-lockdown can be achieved without increasing the transmission of disease disproportionately. Thus, a phased wise approach to un-lockdown is encouraged. We also provide the rationale for using β over Rt values to specifically assess the effect of public health interventions designed to decrease exposure. Copyright (c) 2022: Author(s).
ABSTRACT
The emergence of novel SARS-CoV-2 variants of concern (VOC), in late 2020, with selective transmission advantage and partial immunity escape potential, has been driving further evolution in the pandemic. The timing of mutational evolution and its limits are thus of paramount importance in preparedness planning. Here, we present a model predicting the pattern of epidemic growth including the emergence of variants through mutation. It is based on the SEIR (Susceptible, Exposed, Infected, Removed) model, but its equations are modified according to the transmission parameters of novel variants. Since more transmissible strains will drive a further increase in the number of cases, they will also lead to further novel mutations. As one cannot predict whether there is a viral mutational evolutionary limit, we model a cascade that could lead to hyper-exponential growth (HEG) involving the emergence of even more transmissible mutants that could overwhelm any systematic response. Our results are consistent with the timing, since the beginning of the pandemic, of the concurrent and independent emergence of the VOCs. The current dominance of the Delta variant and the need for additional public health measures indicates some of the risks of a possible HEG. We examine conditions that favor the expected appearance of similar variants, thus enabling better preparedness and more targeted research.