Pandemic In The Lab- The newest expansion for Pandemic that adds a few modules that you can choose to use, but most importantly it allows for the Lab module that makes the game a bit more thematic as you have to do lab research to find a cure for the diseases.
I've never played this game with anyone who didn't fall in love with it after 2 games. It's very easy to learn, but can be difficult to master. At the same time, it's one of those games that is fun to play even if you are losing horribly. Great game for beginner gamers.