Pathogen: Neurax Worm (Of course) Difficulty: Casual, Normal and *Brutal.
Try aiming for a hot, arid, and poor country. (It does not matter if it has an airport or not because of Trojan planes). If you did not start out in one, just restart and try again. Also, have it at 2X speed (You don't have to but that's how I did it).
Send remaining Trojan planes to under - infected countries or non - infected countries.
Most likely you might have problems with the African countries. If so, evolve Heat Resistance 1.
Around 1.5 Billion people infected start working your way up to the Transcendence Symptom. (Neural Breach > Cerebral Tendrils > Frontal Mesh > Immaturity > Mania > Obsession > Devotion > Transcendence)
By now you should be kicking back and enjoying your new pet named humanity slowly conforming to the Neurax Worms rule.
*This heavily depends on your starting country.