It took a few tries, if you count save scumming as repeated tries, with Quijibo's plan sorta, with my own tweaks, but I managed it on Mega-Brutal!
I went for Drug Resistance 1 first, and went for Bacterial Resilience 1 instead of Cold Resistance, then Water 1 as ship preparation for Greenland and Madagascar.
Probably should've gone for Bacterial Resilience first, then Water, then Drug, for the widest range of infectability first...
Avoiding the "animal" transmission traits to keep mutations down, since devolving them costs points, so I want to avoid them as long as I can. I got Insomnia, so I decided to buy Anaemia immediately after in hopes for Walking Dead to trigger.
I made saves often, and reloaded when "Plane / Ship Cleaning Improved" events triggered, and avoided them through enough scumming. That might actually be the thing that saved the run.
Can't save-scum past the Chinese Doctor discovering the virus, and a good idea is to focus on Genetic Hardening immediately after, making sure to save up enough points to buy ReShuffle when at 99% Cure.
I focused on Cold Resistance, then Heat Resistance, to get Environmental Hardening. That likely wasn't a good idea, because I thought that helped me with Arid climates. Wiki says it doesn't, so those points might have been better spent on Heat Resistance to get into Africa, where my last holdouts were.
On Symptoms, I stored up my points until 90 and rushed Insanity. Should have went for the Coma line from Inflammation onwards instead of trying to go from Anaemia to Necrosis and stalling at Hemorrhagic Shock.
Note that the Cure ETA is sometimes inaccurate. It made jumps from 99%, 229 days until completion, and 206,647 Infected, to 100% cure in a few days, all with just the resources of Angola. That's some crazy Dark Horse Victory.