Start as parasite, sell all starting symptoms, upgrade all resistances to 2. Upgrade drug resistance to 4. Upgrade your transmissions, water first. Once each continent/region is infected then start purchasing symptoms, vomiting and sores are good. Fever is better. That's the easiest way to win. You'll win in approx. 200 in-game days.
Alternatively, start with a virus and do the same strategy, except you'll need to upgrade your resistances more and pay closer attention to where ships and aeroplanes visit from your starting region and upgrade resistances accordingly to maximise your infection. Happy holocaust. :)
 "Pandemic 2"){kind=icon}