It is now possible to carry an atomic bomb in a suitcase, or to bring the Internet to its knees from a PC in Bulgaria. We cannot allow terrorists to hide in protected enclaves anywhere on earth. We have seen how hoof and mouth disease devastated Britain. Even with drastic measure of killing livestock anywhere near infected animals, they could not get on top of the epidemic. How much more difficult it would be to control a human epidemic.
Airlines allow new diseases to travel around the earth in hours.
I burst out laughing at the US Immigration service. When they discover a person coming into the USA infected with TB, they immediately put them in strict isolation. The only possible way to deal with disease is to wipe it out globally. You can't leave pockets of it anywhere to restart the infection, even if those pockets are in places where the people have dark skins. Racist attitudes to disease control mean polio and malaria continue to stalk the planet when we had to technology to wipe them out decades ago.