From the article:

[Brantly] said Ebola "was not on the radar" when he and his family moved to Liberia in October.

I wouldn't have been in Liberia in the first place, but if I had been, I would've been on the first plane out as soon as I even heard a rumor about an Ebola outbreak. He could have--the U.S. is aggressive in helping American citizens evacuate from situations like that. The fact he stayed and helped is what makes him a hero.