How can you tell if you have a sinus infection? or how does a doctor diagnose it?

Even so: Even when we do sort it out, recent studies show so many sinus infections are those darn untreatable viruses that making the distinction may not be as helpful as we thought. We ask if illness has been over 10 days, headache and facial pain, tooth ache, high fever, thick colored runny nose and/or cough, worse when laying down with drainage. Does not help distinguish viral vs bacterial though.