Résumé
Self-instigated isolation is heavily relied on to curb SARS-CoV-2 transmission. Accounting for uncertainty in the latent and prepatent periods, as well as the proportion of infections that remain asymptomatic, the limits of this intervention at different phases of infection resurgence are estimated. We show that by October, SARS-CoV-2 transmission rates in England had already begun exceeding levels that could be interrupted using this intervention alone, lending support to the second national lockdown on November 5th.
Résumé
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted more effectively in densely populated areas and omitting this phenomenon from epidemiological models may substantially affect projections of spread and control. Adjusting for deprivation, proportion of ethnic minority population and proportion of key workers among the working population, mortality data from England show good evidence for an increasing trend with population density until a saturating level. Projections from a mathematical model that accounts for this observation deviate markedly from the current status quo for SARS-CoV-2 models which either assume linearity between density and transmission (30% of models) or no relationship at all (70%). Respectively, these standard model structures over- and under-estimate the delay in infection resurgence following the release of lockdown. Models have had a prominent role in SARS-CoV-2 intervention strategy; identifying saturation points for given populations and including transmission terms that account for this feature will improve model utility.