Two flaws in your reasoning. It is the “strong immune system” that killed many of the otherwise healthy victims of the Spanish flu. Google “cytokine storm”.
When a “particularly virulent strain” comes along there typically isn’t ANY acquired immunity in the population. This is why the new strain is so virulent. The DNA and antigens in the new strain are truly novel and might show evidence of development in another species’ gene pool (birds or swine).
steve86 : "It is the “strong immune system” that killed many of the otherwise healthy victims of the Spanish flu.
Google “cytokine storm”. "
Or use Duckduckgo.com
“cytokine storm”, or the bodies own reaction did the most damage.
Notice the number of fatalities among people in their 20's and 30's.
The number of total fatalities affected the social construct throughout the world.
Doubt it ? Check your own family genealogy, or family grave site.