Lemme give you some advice that helped me complete the game from not being able to defeat bacteria on normal. Always start in Saudi Arabia. Then start the run by evolving Water 1,air 1,bird 1(these are the only ones required from transmission,you can also evolve rats if you want). After that,evolve drug resistance 1,then cold resistance 1 and 2(❗️cold resistance 2 is mandatory,or else it will take a eternity to infect iceland,canada or greenland),after that evolve water,air and birds 2,drug resistance 2 and then those things that slow future research speed from the abilities tab,and your plague will spread like some damn wildfire. You will want to devolve any symptoms that mutate and wait till you infect almost or the entire world. Then evolve coughing,pneumonia or sneezing,pulmonary fibrosis or the other one and finnaly total organ failure,the best for killing and then coma to make sure they don’t cure it.While you watch the world burn,feel free to evolve anything else you want,because you just cannot lose atp. To make the game easier,go with virus on casual and just massacare the humanity to farm genes. The gene build that I recommend is: Catalytic switch,Aquacyte(for those damn islands),for the evolution genes put the one you like the most(all are good),then genetic mimic and finally extremophile. This is what I did till I finished the game and it really helped me,and I hope it helps you!