How come you can't get infected por walker blood transmitted via the eyes, nose, ears or mouth? I know you can get infected either por a bite or a scratch. The characters get splattered with blood with each kill but live to fight another day. Thanks!

I think under the premise of this show, the bite floods you with a massive dose of the infection which makes you sick and die. Then is it the dying that actually triggers the change because as the scientist told Rick in season 1, everyone is already infected with the virus itself and it triggers in death. That's also why they do the double kill to someone who hasn't turned yet.

Everyone is already infected with the virus (Jenner said so to Rick). So the bite or the scratch doesn't infect you, because you're already infected, it only gets you sick (fever) and then the fever kills you. Like laylastepford said, the virus gets triggered once you're dead only.