Care homes in the UK were disproportionately affected by the first wave of the
COVID–19 pandemic, accounting for almost half of COVID–19 deaths over the course
of the period from 6th March – 15th June 2020. Understanding how infectious diseases
establish themselves throughout vulnerable communities is crucial for minimising
deaths and lowering the total stress on the National Health Service (NHS Scotland).
We model the spread of COVID–19 in the health–of NHS Lothian, Scotland over
the course of the first wave of the pandemic with a compartmental Susceptible –
Exposed – Infected reported – Infected unreported – Recovered – Dead (SEIARD),
metapopulation model. Care home residents, care home workers and the rest of the
population are modelled as subpopulations, interacting on a network describing their
mixing habits. We explicitly model the outbreak′s reproduction rate and care home
visitation level over time for each subpopulation, and execute a data fit and sensitivity
analysis, focusing on parameters responsible for intra–subpopulation mixing: staff
sharing, staff shift patterns and visitation. The results suggest that hospital discharges
were not predominantly responsible for the early outbreak in care homes, and that
only a few such cases led to infection seeding in care homes by the 6th of March
Sensitivity analysis show the main mode of entry into care homes are infections by
staff interacting with the general population. Visitation (before cancellation) and staff
sharing were less significant in affecting outbreak size. Focusing on the protection and
monitoring of staff, followed by reductions in staff sharing and quick cancellations of
visitation can significantly reduce future infection attack rates of COVID–19 in care
homes.