Yeah, it depends on your immune system, but the point is: every single character in mangas get knocked out by a flu, I was just wondering if that's real or is just some cliche from mangas, you know? I remember when I was in high school if one student got a flu the next day it would be like 7 or 10 students coughing and sneezing in the classroom ( and no, we didn't have the habit of wering mask at all before corona Σ(  ̄□ ̄||)), a weak later everyone was just fine and nobody would miss classes because of the symptoms, Its really interesting how a viral disease may have diferences between two populations.
is the flu in Japan really that strong? You know, here where I live I didn't stay in bed with fever like that since I were 5-6 years old, and I don't know a lot of young pleople that get this bad when they're had a cold, I guess being like that is more common for elderly or infants, but in every single anime or manga that I ever saw if you have a flu you have to stay in bed almost dying.