How will a doctor differentiate viral respiratory infection from bacterial infection? signs are fever cough congestion, no sore throat - 4 days.

Usually easy: Normal w/ viral uri's to have a temp up to 72 hrs. If u have sore throat it's very unlikely to be strep when u also have cough/congestion (not always the case with kids). Flu is peaking now (in us) classic symptoms are high temp congestion, body aches, +\-sore throat or cough. If u r feeling unusually ill or measured temp exceeds 3 days u should be seen (sooner if u have chronic health cond.

Symptoms...: Typically, with a bacterial respiratory infection, the fever tends to be higher and the sputum tends to be discolored from baseline. The white blood cell count is often elevated. With a viral respiratory infection, the fever tends to be low-grade and the cough can be non-productive or clear sputum. However, there is considerable overlap so, if symptoms don't improve over a few days, see a doctor!