Whether the title of this true or not is debatable - but following my third Spanish lesson of the day today, I figured that we don't really know the difference between a few similar words. Don't be morbid. They don't only refer to diseases.
Pandemic - something that is spread across a whole country, continent or the world
Epidemic - something that is extremely prevalent, affecting many people at the same time
Endemic - something that is typical of a certain people or place; native
Aren't you glad that's all cleared up now.