A Population-Based Susceptible, Infected, Recovered Simulation Model of the Spread of Influenza-Like-Illness in the Homeless versus Non-Homeless Population

PURPOSE: To examine the prevalence and characteristics of influenza-like illness (ILI) related presentations among people experiencing homelessness compared to the general population as well as to use the Susceptible, Infected, Recovered (SIR) simulation model parameters β and γ to model infectious interactivity, recovery rate, and population-level basic reproduction number (R₀). METHODS: Using administrative health data from emergency department (ED) visits in the province of Ontario, Canada from 2010 to 2017, an SIR model was used to calculate the R₀ for ILI in both the general population and the population of homeless individuals. RESULTS: From 2010 to 2017, a total of 17,056 homeless and 85,553 non-homeless individuals presented with an ILI to an ED in Ontario. The estimated infectious interactivity (β) was lower while the recovery rate (γ) was longer for infected people experiencing homelessness. CONCLUSIONS: Our results suggest that infections of ILI will result in more secondary cases in the homeless population compared to the homed population. This evaluation of the dynamics of ILI spread in the homeless population provides insight into how illnesses such as COVID-19 may be much more infectious in this population compared to the homed population.