In the early game, try focusing on abilities for your pathogen that can be a bacteria for example (especially for me) as number one, transmissions as number two to quickly take over the world and some symptoms as number three if you need them just so you can have some resistances to environments, drugs and then the cure and you can infect more people easily without having to be fatal towards humans which can be a bad thing due to it potentially making people notice that you exist, and later on or when you're able to infect most or all of the population, focus on the symptoms and abilities even more than the transmissions if you can and/or if you have enough DNA to unlock the stuff, and also when you're done fully unlocking all of the ability stuff by being highly resistant and adaptable to drugs, cold/hot or mixed environments, etc while successfully infecting everyone on Earth, you may or will now have to fully focus on the symptoms to max out as much pathogen lethality as best as you can to make sure that the infected population dies quickly and to make sure that the cure progress gets stopped or atleast slowed down. (I think it can work though I'm not very sure about it, especially when it's applied to other disease types such as the virus, but I hope it can for you, especially also on casual difficulty.)
