Severus in my stories has come to terms with what happened in the Shack and all out blames Sirius, he likes to hate him anyway, lol.
Absolutely yes on the virus idea! I completely agree with that. I see it as a virus on a time-table that lives in symbiosis with the human. Too propagate it 'breeds' during the full moon, taking over the actions and mind of it's human host so that it can infect others in order to continue it's existence. Unfortunately, it goes about in an extremely hard way for the human host. So any werewolves would have a more difficult time with their wolf nature oh about the week leading up to the full moon. But it's not something they can't control if they had been trained from an early age to recognize the symptoms, just like women can recognize the symptoms of PMS.
Greyback, I don't understand how he can look the way he does in the movies, while Remus doesn't. The other think that gets me is where did Greyback learn magic? Or am I mistaken that he knows magic? Was he a wizard already that turned werewolf after he graduated from Hogwarts? Or did he learn his magic from the DEs? I'm kind of curious to his history. I don't think I've read a fic yet on how he got to be the way he is and I don't think I'm the right sort of person to tackle it. He turns my stomach, and someone who's better at that sort of fic would do more justice to the story I'm sure.