Don’t max the drug resistance until they start creating a vaccine, and even after that you might want to just get 3, because they probably won’t finish. Also, after you infect every country, DO NOT get kidney failure. The lethality/points spent ratio is very bad for that one.
To infect every country in the first place, the only thing I can advise is luck. That and wait several seconds after Madagascar closes its ports, because a boat might go in right afterwards. (I have the impossible badge, by the way)