The percentage of routine blood lymphocytes refers to the proportion of lymphocytes in the white blood cells, which is 20%-40% in normal adults; below 20% is a decrease in the lymphocyte percentage and above 40% is an increase in the lymphocyte percentage. Decreased lymphocyte percentage is common in acute bacterial infections such as acute suppurative appendicitis, acute suppurative tonsillitis, and acute skin infections, all of which have a decreased lymphocyte percentage and are often accompanied by elevated neutrophils. Increased lymphocyte percentage is commonly seen in cases of viral infections, such as when influenza virus and rubella virus infections are present. If an abnormally high lymphocyte percentage is accompanied by anemia and thrombocytopenia, it is often a sign of acute lymphoblastic leukemia.