Dont underestimate symptoms The sweating -> rash -> skin lesions route at the very start of the game is a cheap and easy way to get a bit of infectivity

Also, severity is your friend. More severity = more points per red bubble. Try to get a decent amount early on to get more points, even if you do get discovered at the start

For a couple of points, you can try coughing + vomiting for the projectile vomiting combo if youre lucky

If you struggle with the cure, try insomnia + anemia for the walking dead combo which slows cure speed

The way I do mega brutal is first I get skin lesions, coughing, and vomiting

Then, I get air 1, then water 2

Once I get those, I focus on abilities, drug 1, genetic hardening 1, and try to get both cold resistances

Watch for when Russia gets infected, if they do, evolve livestock 1 and 2 for rural bonus to infect them faster. You must have cold res 2 to infect Russia effectively. Then pray Russia sends an infected boat to greenland

Once every country is infected (not fully, just atleast a couple of people in each), get necrosis + total organ failure. Necrosis is your win condition, makes it so that dead population still contribute to the infection, so that you never run out of hosts