in general you should consult your doctor if you think you have a bacterial or viral infection. exceptions include the common cold which is usually self-limiting and not life-threatening. in some cases it's difficult to determine the origin of an infection because many ailments -- including pneumonia meningitis and diarrhea -- can be caused by either bacteria or viruses. but your doctor usually can pinpoint the cause by listening to your medical history and conducting a physical exam. if necessary he or she also can order a blood or urine test to confirm a diagnosis or a "culture test" of tissue to identify bacterial or viral growth. occasionally a biopsy of affected tissue may be required.
how are bacterial and viral infections diagnosed?