Yeah. The nurse should have caught this right away as soon as he or she asked about Duncan about it. (Although he may have lied as he had before when leaving Liberia.)
That said, the person was probably not a nurse but just a barely literate desk clerk, which is normally what does “triage” in a big city emergency room. Half of them have been hired through welfare-to-work programs.
Sorry, it was human error.
It could very well have been be a barely-literate nurse. There are very few native-born nurses these days. Most of the ones I see are third-world.