Was he a coke head too? That is one drug the body - unlike heroin for instance, you don't die from heroin after-effects years after you have kicked the habit - never forgets. The reaper holds feast with all heavy coke users decades after they have given the habit up ... Jeff Porcaro, Robert Palmer, JAE ... Rick Parfitt's numerous heart attacks and by-passes ...
That said, flu can be a serious and tasking disease, I 've had the flu twice myself, the swine flu was extremely severe for about two to three days, yet you recovered quickly from it. But before that I had a regular flu (sometime in the 90ies) and that knocked me off my feet like nothing before or after. I was badly sick, feverish, for two weeks and weak from it for months. Even without a cocaine habit! (I tried it twice in the 80ies, it never did nothing for me except a running nose and numb gums.) Ever since then I take flu shots every year - no desire to repeat the exercise ever again (the flu shots at the time couldn't help agains the swine flu, that is why I caught that from someone in the office). Once you have had the flu, you'll never refer to even a severe cold as "the flu" again.