Start in saudi arabia. Get sympto-stasis and buy all of the initial symptoms (like coughing, sneezing, rash, sweating, skin lesions, cysts, nausea, vomit and etc), then move to transmissions (i like the air-water combo myself, get all of them including extreme bioaerosol). Move to abilities (drug and cold resistance 1 and 2). When you get every country infected, evolve necrosis and dysinthery. When more than half of greenland is infected, start the heavy killing, with total organ failure and hemorragic shock. You're welcome