How do you play the game? Well, first you need to figure out how you want your virus to develop, choosing different pathogens and symptoms in order to affect the global population. You will end up with tons of different diseases at your disposal.
Okay, now what? You cant just solely focus on developing your disease into its most lethal version; youll also need to try and get it to spread through all five continents in the most effective possible manner. You ultimate goal is to wipe out all human life - country by country.