Basically, what happened? I thought I did everything right. The game even told me so and said that no one got infected... so... did the game glitch on me on that one?

Anyways. I do have childrens powders... what do they exactly do for other characters. Does it mean I can only cure them once and that is it? The game is very cryptic about it.

The game is very cryptic about pretty much everything, and I think of it more of an experience than a traditional game, per se.

If you go to Ice Pick Lodge's official website, they clearly state (in a somewhat elitist way, with which I'm completely fine but others may not be) that they want to merge video games with more abstract, contemporary art -- namely literature -- and dilute the borders between video games and "actual arts". They are certain of the fact they don't make games for everyone, and I agree with them.

Just like Beckett's The Unnamable isn't a read everyone will enjoy, so is Pathologic a game not everyone will understand.

[disclaimer] not saying this is your case, just clarifying the cryptic nature of Pathologic and the other amazing Ice Pick Lodge games.

Which character are you playing with? Is Gryph your Adherent? I haven't played with the Bachelor for a long time, but I can tell you for sure that in the Haruspicus' playthrough Gryph's disease is not scripted.

Anyway, you're better off saving those children's powders until Day 12 if you want the best ending. For now you can just give him a strong antibiotic and he will live until the final day, provided you do it every day, and then you can cure him for good.