Three Strikes and You're OUT

Infection with the influenza virus causes massive lung damage, raising endotoxin levels drastically, which lowers orexin levels.
Endotoxin reduces the immune response to many bacterial infection, so those are common afterwards.

Strep and staph bacteria then give you another big dose of endotoxin by causing open lesions.

And then the antibiotics they give you burst the bacteria and release A LOT more endotoxin, which shuts down your orexin production completely.

Low levels of orexin impairs healing and promotes intestinal permeability which allows all that endotoxin to leak into your bloodstream constantly,  finally killing the orexin cells.