Originally Posted by Nunyabiznes
Because they are the main. Just like Lee and Clem.
Kirkman stated that Rick can die before the Walking Dead is over. So him being a main has nothing to do with it. Plus Kirkman also stated that bites leave a wound that is so infected it's 100% fatal.
My question to you is, why do you go against what the creator of The Walking Dead says? Clearly the writer said it was 100% fatal, so according to your logic, which is, that if the writer states so it's true. Then this is now true and you can accept it. Lee is gone. Season 1 was his and Clementine's story, now Clementine will move on and most likely introduce another main character unless we'll be playing as her. Which wo knows, might turn out to be interesting.
Also, the breathing you could hear were his last breaths. Ever been with someone that was dying or maybe a pet that got put to sleep? After the heart stops there is one or two last breaths left.