Why the focus on the flu? Because in the modern age this is the most dangerous pathogen capable of rapidly spreading across the globe in a matter of weeks, possibly infecting and killing millions. And because it constantly mutates, there is no universal vaccine to stop it. These facts alone should concern anyone.
What's educational about this series is that I did not know the how much of it is zoonotic - e.g. capable of spreading from animal to animal including humans. The current 2019-nCoV that started at a wild meat market in Wuhan is only an example of what's possible with the flu. And that should scare everyone.