Mr. Duncan knew he was exposed to Ebola. The more interesting question is

[JimDandy]

22. I suspect he had a case of "hope against hope"

which could be why he flew to the U.S. in the first place and then why he felt reassured that he hadn't actually contracted Ebola after the professional health care workers (to whom he DID tell he was from Liberia, a fact which the hospital has now admitted) released him from the hospital with just antibiotics. People do this kind of thinking all the time when dealing with professionals they trust to know better then them.

Had I been him, though, I would have made sure to tell them that I had transported a sick pregnant neighbor to a hospital in Liberia and that she died of Ebola the day after transporting her.

In any case, the hospital had enough info to have suspected Ebola, and the blame for the additional cases of exposure (and delay in Mr. Duncan's treatment and the delay in identification of everyone he contacted up until he was admitted the second time) after that first visit are squarely on the hospital.