A lethal flu epidemic apparently occurs three or four times a century. The last one I could find with a quick Google search was the 1968-1969 Hong Kong flu, which was a type of an avian flu that killed 750,000 people. So, it would appear that we should be facing another epidemic or pandemic fairly soon. Of course, the recent flues have so far been failures: SARS never really got anywhere on the pandemic scale, and the current avian flu is still something that hasn’t done that much.
In any case, we can all now rest assured that if a pandemic hits us, say, next year, 62 million of the world population would die, with most deaths occurring in the poorest nations. Or that is what this BBC News article says.