Unlocking new game types such as Virus, Fungus, up to Bioweapon
You can unlock the next type by clearing the stage before it on Normal or Brutal difficulty.
Bio-Weapon - Beat Nano-Virus on Normal or Brutal.
Fungus - Beat Virus on Normal or Brutal.
Nano-Virus - Beat Prion on Normal or Brutal.
Parasite - Beat Fungus on Normal or Brutal.
Prion - Beat Parasite on Normal or Brutal.
Virus - Beat Bacteria on Normal or Brutal.
Unlock 3 game cheats
This can be unlocked via completing the game on Brutal.
Cheat Modes: No Cure, No Action and Infinite DNA - Beat all the gamemodes, Bacteria to Bioweapon all on Brutal.
Unlimited DNA when playing Nano-Virus
This simple exploit of current game mechanics makes a joke of one of the harder disease types! (When playing nano-virus, they are aware of and curing your virus from the start) It requires only that you have unlocked (and equip) the 'Sympto-Stasis' genetic code upgrade when setting up your game. Genetic codes are unlocked by winning a game on any difficulty with any virus type. With Sympto-stasis equipped, the cost of symptoms does not increase as you evolve them. The nano-virus has 2 symptoms that actually -GIVE- DNA when you take them, and this virus type has a natural ability where devolving costs don't rise (default cost of devolving gives 2 DNA). These are Insomnia and Paranoia. Simply buy those 2 and then repeatedly devolve/evolve paranoia for unlimited, free DNA.