Published time: 05 June 2020
Authors: Karl Pillemer, Lakshminarayanan Subramanian, Nathaniel Hupert.
Keywords: model, population, SARS-CoV-2, modification, quarantine, isolotaion.
In February 2020, the US outbreak of novel coronavirus disease 2019 (COVID-19) began with a cluster of cases at a long-term care (LTC) facility in Washington State. Since then, 34 of the 40 states with available data report that at least 40% of COVID-19-related deaths in those states have occurred in LTC facilities,1 which provide ideal conditions for rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although the populations in these facilities bear a significant burden of the pandemic, mathematical models that contribute to US national or state policy do not account for residents of LTC facilities separately from surrounding populations in their calculations.2 This Viewpoint explores why it is important to separate projections for residents of LTC facilities and the general population.
Current major COVID models, including mechanistic ones like that from Imperial College London and hybrid forecasting ones like that from the Institute for Health Metrics and Evaluation, assume similar dynamics of SARS-CoV-2 transmission.3,4 Models like these calculate the number of susceptible, exposed, infectious, and recovered individuals (the standard SEIR framework) in an entire population, estimating the chance that individuals of different ages come into contact with one another and accounting for age-based risks of becoming infected or having worse outcomes.
Although this model structure can incorporate protective strategies like school closure and physical distancing, its currently used forms do not capture the dynamics of specific at-risk subpopulations and thus may not capture the complexities of how COVID-19 is spreading in LTC settings. During the Ebola outbreak in West Africa in 2014, modelers and policy makers recognized that existing models needed modification after transmission from deceased individuals was discovered5; that point has now been reached with COVID-19.
The Importance of Long-term Care Populations in Models of COVID-19