Ebola and its sibling Marburg are not going to ever disappear, because they are animal diseases and the animals (probably fruit bats) are not going to disappear. These diseases will always be a problem in Africa.
That is a different issue than unchecked immigration. We could very well get diseases that have never occurred in the US before, or that we eradicated decades ago. We won't get Ebola or Marburg from unchecked immigration, unless we start smuggling in live infected fruit bats.
Thank you.