Let's just magically change the rules...(spoilers)

All of a sudden humans are going to be able to infect other humans using walker blood, guts, and saliva? If this was possible, there are countless people that should have been infected. Most notably Daryl in season 2, looking for Sophia, when his arrow went through a walker and into him. I remember thinking at that time, he's done, but I learned it doesn't that way now all of a sudden it does?make Let's not forget covering one's self with walker guts. No infection, but now.....

Granted I don't know the rules in the comics, but throwing this rule into the TV show, after so many years of the opposite being true, makes no sense. It's cheap and pathetic.