Zero defense as in Flu vs novel viruses are apples and oranges. Talking endogenous defense not exogenous
when you get the flu even as tiny tiny baby, your immune system was gentically coded to have some defenses and recognize innately how to fight that virus
as an adult every time you've ever come into contact with a flu from the time you were a baby to now has given your immune system new data as each set of flu strain from year to year is a slight tweak from the molecular structure you encountered as a baby. So you have antibodies, natural killer cells and macrophages that already know how to dispatch with the invader.
with Novel viruses, they come from an animal strain. Its completely different from human strains. So when it infects the body. There are zero gentically coded procedures for your body to know how to fight it.
its like when an NFL offense first ran a gimmick offense like the wild cat against a defense. at first it was very difficult to defend and even half time adjustments weren't enough
it took weeks of film review to build up the nfl immune response to the new invader
that's how your body works with novel viruses
but just like the flu, people that are old don't have enough time to come up with a defensive plan
unfortunately if you have a body mass index over 25, you have diabetes, you have high blood pressure, you have respiratory illness, you smoke or usd to smoke, you drink too much, you have an immune illness, you are fighting cancer ect. you are at very high risk.
How many Americans fall into those high risk categories?
you also might not have enough time to formulate a defense
a new risk factor
not having a ventilator. That will increase deaths 10x fold once we hit those levels.