The lie was one of omission. Duncan opted to keep his exposure to Ebola to himself. He could/should have provided this critical piece of information to the nurse at triage in the first hospital visit. Because he refused to disclose his exposure, he gambled with his life.
His loved ones are not to blame for not knowing.
The lie was one of omission. Duncan opted to keep his exposure to Ebola to himself. As far as he knew, the woman he was helping had malaria. He was perfectly aware that malaria is not contagious. Malaria is very common in equatorial Africa. I do not see how he could lie when he really did not know.