Mobility restrictions for the control of epidemics: When do they work?

Background: Mobility restrictions - trade and travel bans, border closures and, in extreme cases, area quarantines or cordons sanitaires- are among the most widely used measures to control infectious diseases. Restrictions of this kind were important in the response to epidemics of SARS (2003), H1N1 influenza (2009), and Ebola (2014). However, they do not always work as expected. Methods: To determine when mobility restrictions reduce the size of an epidemic, we use a model of disease transmission within and between economically heterogeneous locally connected communities. One community comprises a lowrisk, low-density population with access to effective medical resources. The other comprises a high-risk, high-density population without access to effective medical resources. Findings: Unrestricted mobility between the two risk communities increases the number of secondary cases in the low-risk community but reduces the overall epidemic size. By contrast, the imposition of a cordon sanitaire around the highrisk community reduces the number of secondary infections in the low-risk community but increases the overall epidemic size. Interpretation: Mobility restrictions may not be an eective policy for controlling the spread of an infectious disease if it is assessed by the overall final epidemic size. Patterns of mobility established through the independent mobility and trade decisions of people in both communities may be sucient to contain epidemics. Funding Statement: Baltazar Espinoza and Carlos Castillo-Chavez were funded by the National Security Agency (NSA Grant H98230-J8-1-0005) and by Data Science Initiative at Brown. Charles Perrings was funded by NSF grant 1414374, and by UK Biotechnology and Biological Sciences Research Council grant BB/M008894/1. Declaration of Interests: All authors declare no conflicts of interest.