The article at: Ebola Patient 'Knew' He Had Virus, Flew to US to Survive

Only Mr Duncan knows, but he may be in denial. Cognitive Dissonance (when what you think you know clashes with reality) also plays a role; in the face of an Ebola epidemic where he lived, he refused to admit to himself that he could have Ebola and wouldn't admit having been exposed to anyone, possibly including himself. Possible, not a fact...

The CDC and WHO need to take that human flaw into account with their screening procedures.