the short is: alien race f's up a non trivial percent of the human population with a virus.. most die. what neat is the mish-mash of history with a new minority of deformed humans. i think it starts in ~1947 running through the 90s.
British writer Neil Gaiman met with Martin in 1987 and pitched a Wild Cards story about a character who lives in a world of dreams. Martin declined due to Gaiman's lack of prior credits at the time. Gaiman went on to publish his story as The Sandman.