From the Steam page:
"Plague Inc: Evolved is a unique mix of high strategy and terrifyingly realistic simulation. Your pathogen has just infected 'Patient Zero' - now you must bring about the end of human history by evolving a deadly, global Plague whilst adapting against everything humanity can do to defend itself."
I've played the free version on my tablet. It's a blast! Their new version is still in the works and they have an early access offer available. I highly recommend it.