Hospital admission, facility-based isolation, and social distancing: An SEIR model with constrained medical resources

COVID-19 is a highly contagious disease that has spread to most countries at unprecedented transmission speed. Medical resources and treatments provided by the healthcare system help reduce the mortality rate and spread of COVID-19 by isolating infectious individuals. We introduce a modified SEIR model that considers individuals access to limited medical resources to characterize the central role of medical resources during the pandemic. We discuss how the three hospital admission policies (hierarchy, mixed, and Fangcang healthcare system) affect the spread of the disease and the number of deaths and infections. We find that the Fangcang system results in the least number of infections, deaths, and occupied beds. When hospital capacity is relatively high or the transmission rate of the mildly infected patient is not ignorable, a mixed system can lead to fewer infections and deaths than a hierarchy system, but greater numbers of occupied beds. This occurs by preventing disease transmission to a great extent. The results are confirmed by our surveys with healthcare workers in major hospitals in Wuhan, China. We also investigate the performance of the three healthcare systems under a social distancing policy. We find that the Fangcang system results in the largest reduction in infections and deaths, especially even when the medical capacity is small. Moreover, we compare a one-time off policy with a bed trigger policy. We find that a one-time off policy could achieve the similar performance as bed trigger policy when it is initiated neither too early nor too late.