You can easily spread the virus in 80-90 days by this following steps:
1. Set the visibility stat by two or zero (clear out all lethality).. you may leave the immune system checked
2. Start adding points in infectivity option by spend the points in transmission... pick waterborne + airborne first because its will spread easily. then Add incubation, survivability and so on
4. When you have more points... spent all the points on transmission
5. Once the infections spreads nearly 60% begin spend the points on pick immune system, coagulant, hemorrhaging (it's least visibility but it's more lethal)
6. I will pick the most obvious symptom like sneezing and coughing in later stages.
7. Once you noticed every part of the regions has been heavily infected. keep going even you'll get notification says something like, one or more country has closed their public border bla.. bla..bla... just continue... because it's already too late for them to close the borders... the population has been infected.. hehehehe!
8. The breaking news will way "It's the end of the mankind"... and you know why ;p