You don't poop when you got appendicitus
Which proves Volko doesn't have it. He's been having diarrhea.
He most likely has a mild to medium case of that newfangled H1N1 stuff.
It's not too severe, because severe H1N1 usually gives you MASSIVE stomach pain, extreme fatigue, dizziness, and so much diarrhea, you'll probably be on the toilet for hours and hours.