When you give blood, often the “wrong” answer will just have them ask a followup after you submit the questionnaire. Like there is one asking if you had recently visited any of a list of countries of concern. I selected that I had because of a trip to Mexico, but I was still able to give blood that day because when they later asked which region, the one I had visited was considered safe.

I expect if you had been bitten by a mosquito in a place where that isn’t a significant concern and developed no symptoms other than the itch, you would probably be approved to donate. Receiving plasma is less dangerous than receiving blood so I would be surprised if the safety evaluation is more strict.

Riot actually has short stories, comics, and a few books on the lore of the world. It doesn’t show up in the game beyond voice lines, but some of the broad strokes of the Arcane story had been all but confirmed for years. Legends of Runeterra is also a card game set in the same world that expanded on things by letting champions talk to more minor characters (other cards in that case). And they are working on an mmo that will probably dive into the lore much more.