What you said! Unless they do have some kind of immunity being from the region. Either way, they were "hidden" away for some reason. Was it because they were sick or because they were not sick?
“Everybody’s okay,” said Aaron Yah, who is in quarantine along with other relatives of Duncan. He said that no one, including Duncan’s girlfriend, has shown any signs of infection
Maybe the Post is covering for the regime as they usually do. But the deaths of these people would be hard to hide. The simplest explanation is that they were lucky and Youngor Jallah in particular made them take precautions. She knew it was Ebola although she didn't admit it at first.