So, I was trying to do this achievement, and I couldn't get it. So I went to Google, and found this guide. It's for doing the regular Virus on Mega Brutal, but good god, it worked wonders on Casual for an easy pop. I beat it in 480 days! (Results may vary)
"The Virus will typically lead itself - it is fast and brutal, and really needs only minimal guidance. Once you have maxed out the Viral Instability line, your plague will be mutating left and right.
Starting Country: Saudi Arabia. Offers close proximity to other countries and has both air and ship access.
Purchase the following symptoms and abilities when you can (skip if mutated):
1. Bird 1
2. Water 1
3. Air 1
4. Water 2
5. Air 2
6. Cold Resistance 1
7. Drug Resistance 1
8. Cold Resistance 2
9. Drug Resistance 2
10. Viral Instability 1
11. Viral Instability 2
12. Viral Instability 3
(Wait until all countries infected)
15. Immune Suppression
16. Total Organ Failure
Just be wary of making your disease too lethal too soon - if a country is dying faster than it is spreading the disease, devolve some of your most lethal symptoms. You're not going to be hurting for DNA at this point."
ALL CREDIT IMAGINABLE GOES TO: Tycho [Forsythe]
from the Steam Community. http://steamcommunity.com/sharedfiles/filedetails/?id=233828...