The routine blood test can refer to the values of white blood cells, lymphocytes and neutrophils to determine bacterial or viral infections. 1. Bacterial infection: Usually, in bacterial infection, the routine blood test can find that the white blood cells are elevated and the proportion of neutrophils is increased. 2. Viral infections: In viral infections, the white blood cells may not necessarily be elevated, but may be in the normal range or lower, and in most cases the percentage of lymphocytes will be increased. However, it is not possible to directly determine the type of pathogenic microorganisms from the routine blood test alone. Clinically, it is recommended that patients with suspected viral infections continue to cooperate with the doctor for viral nucleic acids, specific antibodies or antigens, and those with suspected bacterial infections need to undergo a blood culture test. Common viral infections include influenza virus, rotavirus, etc. Bacterial infections include Staphylococcus aureus and Streptococcus pneumoniae. Patients should consult with their doctors after getting the test report to avoid the psychological burden of misunderstanding, and cooperate with their doctors for active treatment if necessary.