Cold is one of the most common diseases in clinic. For cold caused by viral infection, the blood test mainly shows that the white blood cell count is decreased or normal, and for cold caused by bacterial infection, the white blood cell count is elevated, as follows: 1. Viral infection: Most of the colds are caused by viral infections, including rhinovirus, adenovirus, respiratory syncytial virus, and coxsackie virus, etc., and the blood test caused by viral infection mainly shows that the white blood cell count is normal or low. 1) Viral infections: Most colds are caused by viral infections, including rhinovirus, adenovirus, respiratory syncytial virus and coxsackievirus, etc. The blood picture caused by viral infections is characterized by a normal white blood cell count or a low white blood cell count, but of course, the proportion of lymphocytes is also elevated, while the proportion of neutrophils is low. 2) Bacterial infections: If the cold lasts for a long time, and a bacterial infection develops secondary to the cold, it may be manifested as an increase in blood picture, such as an elevation of the total number of white blood cells, or an elevation of neutrophil proportion.