One of the things I don't understand is not one single person in the group even remotely mentions to Herschel the fact that they were at the CDC and they pretty much knew what the "disease" is/does.
Herschel apparently believes that it's possible to cure people who are suffering mortal wounds, fatal blood loss, and their organs hanging out. And he believes all this despite being a doctor. (Yes, I know what kind.) His medical knowledge should inform him what is and isn't possible.
It doesn't matter what you tell him. Denial isn't just a river in Egypt.
I realize that but it is much easier to reason or plead your case with someone when you present them with cold hard facts.