"Remember, passing infection without airborne spores is pretty hard so unless there was a specific event where Ellie bit someone hard enough to draw blood, it is unlikely that anyone would necessarily have thought of it."
When is it ever stated that that is a parameter of this fictional disease? I'm talking in-game, not your own assumptions. There are monkeys in the science lab that aren't "infected" but they are carriers, and one of them bites the scientist and infects him. Then Joel says "good thing we stayed away from those monkeys." They're still a danger. Ellie bites enemies (hard) when they grab her all the time, and you can run away without killing them. Are we to assume they all ended up turning?
In-game, inside the Boston skyscraper. Joel was scratched by a Clicker bad enough that it took a chunk out of his HP bar. No-one even questioned if he was infected once.
In-game, after Bill's rescue and he's confirming Joel isn't infected. He only asks if he has any bites.
In-game, in the Boston subway station; Joel is shocked that Ellie is breathing spores without a hint of problems.
In-game, in the East Tunnel, Tess is worried of the slightest crack in Joel's mask because spores are that infectious.
Do you want any more?
Onto the question of Ellie's bites - We don't know if those guys ever turned. It was never specified one way or the other, so it is entirely up to the player's discretion how they view the outcome. That's the point that I'm making. It wasn't important enough for Naughty Dog to confirm or deny.