Glory
If you become an epidemiologist, you're either going to be solving difficult problems or helping people. Most of the time, both. Hopefully that's your jam because if it's not, you just went through a truckload of school to wind up mighty disappointed.
While programmers work tirelessly squashing bugs for Fortune 500 companies, you're going to be helping to squash real, in your face, super dangerous bugs for a fortunate 500 countries. Well, there aren't that many countries, but if there were, you'd be there.
Become an epidemiologist and you'll be doing good. You'll be doing so much good that you'll be doing good by accident. You'll probably wake up one morning determined to not do good just for a change of pace, and then accidentally save .09% of the population of Australia without even realizing. Enjoy it.