Evaluating the Risk of Reopening the Border: A Case Study of Ontario (Canada) to New York (USA) Using Mathematical Modeling

Many countries have adopted border closures and other jurisdictions (provinces, states, cities, etc.) to control the spread of SARS-CoV-2. Such measures have significantly restricted population movement and have thus led to immense economic and social fallouts. We build a Susceptible-Exposed-Asymptomatic- Infectious (prodromal phase)- Infectious (with symptoms) -Recovered (SEAIR) model with a household structure to investigate the potential of a safe reopening of a border, which can control disease spread but also allow for economic growth. We focus on the Ontario-USA border, considering an opening date of September 21, 2020. In addition to the instantaneous reproduction number, we also define a novel risk indicator by calculating daily new infections’ percentile to inform risk levels promptly. Under ideal conditions, assuming extremely efficient border testing and strict traveler adherence to quarantine policy, the Ontario-USA can be reopened for a maximum daily number of 500 travelers entering Canada. A number exceeding 500 will stem an uncontrollable spread of the virus. Additionally, the current quarantine policy may not be sufficient under specific scenarios; hence testing measures at the border must be extremely efficient. Reopening of the Ontario-USA must consider the potential for disease spread (which can overburden healthcare resources) and economic growth. If a reopening plan is implemented, the local government must limit the number of daily entrances to 500 and enforce a mandatory quarantine, which may need to be stricter than current policy practice.