bavarian,
You MUST attend the interview whether or not the day could be the last day of your life.
Many People are waiting for years to get their interviews done.
as other members said, you still got a few more days to feel good. Drink plenty of energy drinks, fruit juice, glucose water, Coconut water, Kebabs. on the day of your interview, have at least one Tylenol, this will kick out the pain for a 4-5 hours. There is no option to let the visa office know at this stage that you got sickness and you wouldnt be able to attend the interview. go to VO on that day and your first thing to report the office that you might need a sick bed ( keep all the medical reports and docs prescriptions with you) while the VO would be conducting your interview.
They are human as well, they too get flu and stuffs. they will understand.