I think the whole coughing thing may be getting blown out of proportion. We've heard a few people turn and never once was there coughing (unless they were coughing up blood due to a wound). Don't read to much into it, Burt got his finger cut off and Shirley destroyed and now he's trying to kill Scratch with his dick (whether it be skull fucking or 'pulling the trigger with his dick'). He's been through a lot, and when he was first picked up by Angel and Saul, he was coughing then too. Victor smokes as well. Nothing there to make anyone wonder, I think it's just coughing and nothing more. This is like hearing the faint sound of a zombie farting and then debating on whether the zombie fart could float into someone's nose and change them.