The spanish flu refers to the 1918 flu pandemic that killed 50-100 million people which was about 3-5% of the world's population. So the big difference is that it's much deadlier than season flu which can kill 250-500K today (versus 210 M which would be 3% today). It's not clear why this flu was much more deadly than other flu seasons.
Answer:Spanish flu caused a major pandemic. Flu on the otherhand doesn't have pandemic because we have a vaccne for it. It also isn't as deadly as the Spanish Influenza.
