People also underestimate the danger of the flu. The flu kills people every year, and that's the mild, endemic one. Only reason it doesn't kill more is that we vaccinate at risk groups and people at high risk of spreading it. People sometimes call other things the flu, but if you get the real thing you know it.
We've avoided several major flu outbreaks because we look for them and take the threat seriously, and frankly, got lucky.
Influenza in the USA does 2x 9/11s a year.