An Epidemic Mobility Model with Symptomatic and Asymptomatic Individuals Allowing Variation of Contact Rates Between Individuals and Across Regions

The control of contacts among individuals and across regions is of paramount importance to understand the dynamics of infectious diseases. In the current COVID-19 pandemic, many infectious individuals are asymptomatic, thereby raising the question as to whether limiting contacts with infected individuals displaying symptoms is sufficient to control the spread of the disease. To this end, we have developed a mathematical model, called SAIRD model, that includes susceptible individuals (S), asymptomatic infectious individuals (A), infectious individuals displaying symptoms (I), individuals who recovered (R) and deceased individuals (D). The model also includes mobility of individuals across geographic regions that accounts for inter-region travel patterns. We have considered 3 regions characterized by different inter-individual contacts. Specifically, no limitations are adopted in region 1, limitations are adopted only for symptomatic individuals in region 2, and limitations are adopted for both asymptomatic and symptomatic infectious individuals in region 3. In the absence of inter-region connection, the model predicts similar disease dynamics in regions 1 and 2, whereas region 3 experiences a notable lower number of infections and death. These results suggest that controlling inter-individual contacts in both asymptomatic and symptomatic cases is essential to contain the disease dynamics. Furthermore, the model predicts that controlling inter-individual contacts without controlling inter-region connections may nullify the gains.