Available online 10 October 2022, 100640
Highlights•We present a novel method to extract and analyse initial exponential outbreak phase.
•Additionally, the method allows the analysis of outbreak social distancing response.
•We fit the SCLAIV+D model to US Combined Statistical Area (CSA) to incidence data.
•We extract values of R0 and curve flattening index for each US CSA under analysis.
•We cluster the CSAs accordingly, observing two response groups (weak/strong).
AbstractWe investigated the initial outbreak rates and subsequent social distancing behaviour over the initial phase of the COVID-19 pandemic across 29 Combined Statistical Areas (CSAs) of the United States. We used the Numerus Model Builder Data and Simulation Analysis (NMB-DASA) web application to fit the exponential phase of a SCLAIV+D (Susceptible, Contact, Latent, Asymptomatic infectious, symptomatic Infectious, Vaccinated, Dead) disease classes model to outbreaks, thereby allowing us to obtain an estimate of the basic reproductive number R0 for each CSA. Values of R0 ranged from 1.9 to 9.4, with a mean and standard deviation of 4.5±1.8. Fixing the parameters from the exponential fit, we again used NMB-DASA to estimate a set of social distancing behaviour parameters to compute an epidemic flattening index cflatten. Finally, we applied hierarchical clustering methods using this index to divide CSA outbreaks into two clusters: those presenting a social distancing response that was either weaker or stronger. We found cflatten to be more influential in the clustering process than R0. Thus, our results suggest that the behavioural response after a short initial exponential growth phase is likely to be more determinative of the rise of an epidemic than R0 itself.
AbbreviationsCSACombined Statistical Area
NMB-DASANumerus Model Builder Data and Simulation Analysis
SCLAIV+Dsusceptible-contact-latent-asymptomatic infectious-symptomatic infectious-vaccinated-dead
KeywordsCOVID-19
Curve flattening index
Epidemiological modelling
R0
Social distancing
© 2022 The Author(s). Published by Elsevier B.V.
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