Colds are all caused by viruses, but some colds can be secondary to bacterial infections, which can be determined initially by symptoms, doing blood tests, and treatment modalities. 1. Symptoms: Colds caused by viral infections often have symptoms such as runny nose, sneezing, chills, low-grade fever, coughing up white mucus sputum, and muscle aches and pains. When secondary bacterial infection occurs, symptoms such as yellow runny nose, sneezing, nasal congestion, fever, chills, coughing up yellow mucus sputum, sore throat, etc. often appear. 2. Blood test: In blood test, for colds secondary to bacterial infections, there are usually increased white blood cells and neutrophils, and the higher the increase, the more serious the bacterial infection; for colds with only viral infections, there are usually increased lymphocytes. 3. Treatment: Colds with secondary bacterial infections are usually treated with antibiotics such as amoxicillin capsules and ampicillin capsules under the supervision of a doctor; while colds with only viral infections can be treated with antiviral drugs such as ribavirin capsules and oseltamivir phosphate capsules orally under the supervision of a doctor. To distinguish whether a cold is only a viral infection or a secondary bacterial infection, you need to go to a regular hospital in time to do the relevant examinations to determine, and actively cooperate with the doctor’s treatment.