Penumbra remembers me to Lost

[jamhaw]

Correct me if I'm wrong but you guys are assuming it is a virus or infection, which I have understood it is not.
The Tuurngait were ancient spirits who flew into people and possessed them. The whispers were caused by the Tuurngait spirits being nearby (when at the artifacts, when Spider Hater was killed etc.). So when Philip first entered the mine the whispers were caused by some Tuurngait checking him out.
Later in the game Clarence (seemingly by accident) possessed Philip and started manipulating his senses. Endgame you find a chemical cure which rejects some sort of virus though, but I'm guessing the virus if existent is a by product after infection (rather than something that infects a person and then escalates into a Tuurngait possession). It's also possible that the antidote rejects spirits (possibly made from one of the around 80 "substances" mentioned and unmentioned) and doesn't at all neutralize a virus.
That's what I think anyways.

I thought that they hive minded aliens like the zerg.