my only problem with it is when it comes up at the worst possible time and there is no possible way to prepare or prevent it from ruining you.
for instance, when you first spawn, and have yet to establish any trade routes to anyone else but your own cities, yet the plague STARTS in your nation, thus spreading to every new city, destroying the troops you spawned with, not spreading to anyone else because you haven't made any foreign trade routes yet, and basically ruining your game before you can even settle down. This happened to me once with Japan, Russia, and Mali, literally a few turns after I spawned, and I had to restart all three games.