2. Cure? Not possible without the right materials. Duncan technically"know" where that is and what is it - if the mission to findit was successful.
3. You probably won't be immune. Immunity was limited to Caucasians for the most part. This has more to do with the history of the Plague and how it came to exist and spread. In other words, if you get exposed,you die. There was a rumor that the Plague was bioengineered by Neo Nazis or White Supremacists. That is false however.