Answer:

Most upper respiratory infections and bronchitis are viral infections. Bacteria usually cause pharyngitis and sinusitis, and pneumonia is usually bacterial but sometimes viral.

Sometimes we try to say that if the secretions are purulent (thick green) that is bacterial. But this is not true. Some with all of this are viral and some relatively nonproductive infections are bacterial.

Most viral infections will resolve in one to two weeks. Many bacterial infections will also resolve on their own. Strep, as in strep throat, should be treated with antibiotics in order to reduce the risk of rheumatic heart disease/fever or kidney disease.

Otherwise we treat bacterial infections that don't seem to be clearing up on their own or are associated with too many symptoms.

For more information, visit theCold & Flu Survivors' Guide.