We've had at least two pandemics since 1918. Why didn't as many people die?
Better medical care, better sanitation. The reason flu starts in China is that people still live in close proximity to ducks and swine.
Bird flu is nothing new. The fact that it infects people may not be new, either. The higher death toll may be a result of the fact that people are now looking for it.
Apparently you haven't read much about this topic.