I have not used any afflictions in my game as of yet, but the party will shortly be going through a festering bog, which if normal mosquitos don't give them a disease, the stirge or some other creature may.
Say they fail any related saving throws for the disease. Do the PC's somehow know they have the disease, or is it, understandably so, something they wouldn't notice unless there was a large sudden effect (looking at you blinding sickness)
If they PC's don't know, do you tell the players and hope they don't Meta, or do you hide it from them as well? And for the saving throws, do you roll them in secret, or have the players roll them as usual? I am just unsure of what to tell the players vs keep to myself, and what the PC would/should know.