 CHAR: When Ellis shoots the original zombie in the head with the  shot gun, the blood spatter hits him in the face. When he wipes it  off he pulls the blood down across his face and mouth. When he  speaks you can see the zombies blood on his teeth. Earlier in the  movie, Nightingale tells a character not to put something in his  mouth cause it had infected blood on it. If this is the case, the  blood that got in Ellis mouth would have infected him.