2 0 0To get this you need to get your disease to have the Diarrhea and the insanity symptoms. The pop up informing you of this combo won't show up immediately so you need to have both of these symptoms active for a little while before you get the achievement.
1 0 0Evolve "Diarrhea" and "Insanity" to eventually unlock in any Standard scenario (Bacteria, Virus, Fungus, Parasite, Prion, Nano-Virus, Bio-Weapon).