Agreed. There should be a moat with alligators protecting the United States on its long and perilous border with Sierra Leone...
You do realize it's perfectly possible for an infected person to just hop on a plane in Freetown and be in New York or another major American city -- completely legally -- in a few hours? That's how we'll get it over here -- not across the Mexican or Canadian borders.
Considering that Islamic fanatics have no problems blowing themselves up and continuing to whittle away at Western civilization, it’s not difficult to imagine someone being provided with a way of self-infection after reaching this country whether by tip toeing through the tulips to cross the border or arriving in a conventional manner and demanding a pat down from the TSA.
Build it and they will come applies.