Just the basic respiratory infection you just gut out for a shitty week.

If it goes “long”, which seems to mean spreads to other parts of the body after it first lands in the lungs, it seems to be that there’s a week break after the initial symptoms, then the new ones show up, which vary based on where the infection spread to

If you’re suddenly really drained of energy, in my case I reasoned out that it was some shortfall in aerobic energy generation (from reacting blood sugar with oxygen), and taking creatine, which enables anaerobic generation (from stored fat) brought me back to function, so I guess consider that.