Is the "Red Death" a real disease that is now dead, or is it symbolic of Death itself?

The red death in the story "The Masque of the Red Death" is probably a reference to tuberculosis, a disease that claimed Poe's mother.  It is marked by coughing up quantities of blood as the victim's lungs become so congested that he cannot breathe and dies struggling for air. That is why he called it the red death, because of the blood.  There was no cure for this disease, also known as consumption, in the past. 

I think that Poe combines the basic idea of TB with the intensity of the Plague symptoms for effect.  People die within a half hour in the story, I think, for dramatic effect.

Now, TB is a disease that people are vaccinated against and in the event of infection, it is treated with antibiotics. It is a bacterial infection and therefore responds to antibiotics.