1) choose virus
2) start in any country
3) buy sneezing only and sell if you had any other. If you started with it great.
4) Buy cold 1... heat 1 AND 2.. and moisture. 4) Wait until a couple of countries are infected (4-7) and then sell sneezing and buy rodent transmission. Trust me. Rodents travel on ships and that's the only way to get Madagascar. After using rodents, I got Madagascar infected EVERY TIME on both modes.
5)After most of the countries have been infected, buy EVERYTHING IN TIER 1 along with pulmonary edema, fatigue, and diarrhea in Tier 2 and hypersensitivity and kidney failure in Tier 3. Don't unlock Tier 4.
6) Wait and earn your badges :) I got my first impossible this way.
Trick to getting madagascar? Follow whatever steps you want to at first.. but get rodent transmission and heat II after infecting a few countries!! That's how I got Madagascar!
 "Pandemic 2"){kind=icon}
 "Dolphin Olympics 2"){kind=icon}