Here's something that could help getting the impossible badge:
I've used sneezing+fever in the first country to spread the desease faster.
WHen a second country its infected I've sold fever.
I waited for 9 infected countrys before selling sneezing.
In DAY 17 all countries were infected.
All the rest I made equal the guide showed in comments.
 "Infectonator : World Dominator"){kind=icon}
 "UPGRADE COMPLETE!"){kind=icon}
 "Pandemic 2"){kind=icon}