Low routine blood leukocytes in fever are mostly seen in viral infections. In viral infection, the total white blood cell count is reduced, the lymphocyte ratio is normal or slightly elevated, and the neutrophil ratio is not elevated. Anti-viral drugs can be applied for treatment, such as oseltamivir, ribavirin or anti-viral drugs from traditional Chinese medicine, such as cold and flu spirit and Lianhua Qingfei capsule. A decrease in leukocytes may also indicate a severe infection. In severe pneumonia, fever, cough and even difficulty in breathing may occur, and a low total leukocyte count and a decrease in platelets in laboratory blood tests suggest a severe infection. Decreased leukocyte responsiveness, causing a drop in white blood cells.