I had the flu when I was in my early twenties and it’s not trivial, not even in a fit, healthy, young person.
I wasn’t sure I could make it as far as the toilet to pee. Every bit of me hurt, the room swam around me, and dream imagery swirled in front of my open eyes. It was wretched and would have been terrifying if I hadn’t been too ill to care.
I was lucky because I made a full recovery.
Much later on in my life, my fit, healthy, adult son got the swine flu. It left him suffering from CFS/ME.
Flu really isn’t something you want to mess with.