Leaving aside the reductionism, the difference is that we are already seeing the effects of the "bad weather" and we all lived through [1] (and, to a point, are still feeling the effects of) the "flu". No "ifs" about it.

There's no need to worry about a threat that has been theorized for 70 years (and may very well never happen) when there are actual, real catastrophes happening right now.

[1] Well, except for those who didn't make it through. They are not here by definition, but their memory is still fresh.