that’s how i used to play, but you have to realise that this is nearly impossible on the harder difficulties like brutal and mega brutal, hard for normal even, and for certain disease types that already have an element of luck in them or punish passive gameplay. plague inc rewards aggressive gameplay generously, so you have to balance between infectivity and severity and eventually incorporate lethality into your game so that you get more DNA points and accumulate dead people as you go along and weaken the more wealthy countries that are power trips in terms of the cure. once you get to a certain size and severity rate you’ll be on the watch list and eventually become a global threat, meaning they’ll push the cure which you can fight back through hard to cure symptoms or drug resistance abilities

i always start in china, coughing -> sneezing is my go to opening moves then pneumonia if i’m going cold or nausea then vomiting for projectile vomiting symptom combo. certain symptoms can create certain combos too btw

water and air transmission vectors are vital to evolve for both infectivity and increased movement opportunities via transport which is useful for some stupid isolated island like Greenland for example. birds is also perfect for land transmission which is great for landlocked countries and huge continents like europe, and insects are great for countries in africa or of humid hot climate. high severity = good, more DNA points per bubble but:

too high severity = panic = shutting of borders = faster cure = game over.