The majority of colds are caused by viral infections, with only a very small portion caused by bacterial infections, or accompanied by bacterial infections. The distinction between viral and bacterial colds is primarily made from the following two aspects: First, in terms of clinical symptoms, those caused by viral colds are mostly short-lived, usually healing quickly within about a week, while the clinical symptoms caused by bacterial colds tend to persist longer, often exceeding a week. Secondly, in terms of blood work, viral colds mostly show normal results, or a lower white blood cell count; whereas bacterial colds often exhibit an increased white blood cell count, or an increased proportion of neutrophils.