Early-phase decoupling between population mobility and death rates

Reductions in human mobility have been a major strategy in controlling COVID-19 transmissions. However, analysis of publicly available data has revealed decreases in COVID-19 death rates that precede mobility changes. This suggests that, in some regions, there are mobility-independent factor(s) slowing COVID-19 deaths. Given the disproportionate impact that COVID-19 has had among nursing homes both in the US and in other countries, we hypothesized that this high-risk population might have dominated early changes in mortality rate. Simulations of a two-population SEIRD model, where one population is more vulnerable, reveal that early-phase decoupling may occur if susceptible individuals in the more vulnerable population are depleted before mobility changes can occur. More work is needed to determine whether mortality in nursing homes explains regional early-phase decoupling.