Closing borders would be of no benefit either. It would be impossible to shut down trade, prevent citizens from returning to the country, etc. That would shut down the entire economy and enormously magnify supply chain problems by ending imports—including all health-related imports like drugs, syringes, gowns, everything. Even at that, models show that a 90 percent effective border closing would delay the disease by only a few days, at most a week, and a 99 percent effective shutting of borders would delay it at most a month.
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