AIUI anybody who gets the flu didn't have immunity to that strain.
YES I think the Chinese Coronavirus AND "COVID-19" are overhyped, possibly for political ambitions; nevertheless this plague worries me on a few points:
1: Novelty: Influenza is all over the world. People talk about "flu season", but "flu season" in the world is like "Vodka Season" in Russia. (starts 1/1, runs to end of year). COVID-19 started in ONE point, and is world-wide now. In the next years, when Chinese Coronavirus (CCV) is not novel, it'll start in multiple places like Flu does, with slightly different strains here vs there. There will be vaccines for both, they will have varying effectiveness. This is a bit scary in its own right.
2: Communicability: CCV is much more efficient at propagating to new hosts than Influenza is. R-Nought for flu is like 1.3, for CCV is like 3. The effect of this is that in the time it takes influenza to go from 1 person to 14, CCV goes from 1 to 59,000. In the coming years, when there are multiple strains of CCV erupting from multiple locations, this could be quite damaging to nations and economies.
3: Lethality: Influenza appears to be lethal in .1% of cases, CCV appears to be lethal in 3% of cases averaged out. We don't really know this because China lies about its case load, Italy has some unusual characteristics (advanced age of society, greater incidence of underlying lung problems from smoking, intense import of infections from China to textile industries in Lombard region, etc), and the disease is too damned new to really boil the lethality down as we have with Influenza.
4: Virulence: the 1918-1920 Influenza plague could kill in a few hours. Modern Influenza kills (generally) in a few days. CCV kills rapidly, but it is too new to be certain if it is a few hours, a few handfuls of hours, or a few days. Current impression: if it kills it does so quickly, in hours.
5: Repeatability (I got it once but I'll get it again): Too little is known here for me to guess. Influenza mutates so rapidly that if you get this year's version, you'll be immune next year just from having it this year. However, next year will bring you at least one "new" strain you're not immune to. With CCV, it's too new to tell.
6: Side effects: Permanent lung damage? More susceptible in the future? Dunno.
I don't want to hype for panic's sake, but the enemy is deadly, and we don't have much to use against it.
Gnomey, please correct my Layman's Misunderstandings if you would please.