system
Given the following post, respond as if you're commenting on Reddit:
human
[The last of us] The infected infect people through biting, so how hasnt Joel been infected when he always punches them in the mouth bare handed.

I mean, has he really never even chipped his knuckle on their tooth HA!HA!HA!
gpt
Its spread by Fungus and Elle is outright immune to it.  Makes some sense that the survivors are less susceptible to the fungus than most people.  

Black death scoured Europe, but there was at least one village that was immune to it because everyone there had a genetic abnormality that prevent the disease from working on them.  They are also functionally immune to aids as the amount required to infect them is over 1000 times normal.  That said, they have some other issues (I believe their lifespans are less than average).  This is probably what Elle is, she's not 'immune' but the scenario that she actually contracts the zombie fungus doesn't really exist(the sample size being delivered by a zombie bite is so great that the zombie is basically finished his meal before she would become infected).

Joel isn't immune, but he probably likewise requires a significantly larger sample size than a normal person would so he can get by with punching the zombie's in the mouth without catching the disease.