They Are Billions is a Steampunk strategy game set on a post-apocalyptic planet. Build and defend colonies to survive against the billions of the infected that seek to annihilate the few remaining living humans.
If you pirated the game read this first
0.8 apparently added a feature for pirated games whereby your housing gets infected regardless of your defenses rather shortly into your game play. There have been a number of posts asking if this is a bug or if the developer is trying to prevent pirating - I think it's safe to say it's the latter.
We Are Billions Torrent
Future posts asking for help or asking if it's a bug will be removed.
If you did pirate the game and then bought a copy that feature might still pop up. Hopefully someone here can tell you how to completely wipe your current install (most likely removing any progress you made) and then do a fresh install, but I don't personally have experience doing that.
Edit: If you have never pirated the game but have encountered this more than once, post it here and hopefully the developers read it. Speculating, but it might be an unintended consequence of the anti-piracy code.