High fever and low white blood cells are usually seen in the following situations:1. The patient usually has a normal white blood cell count. If the patient combines with viral infections, such as influenza, parainfluenza virus, cytomegalovirus, herpes simplex virus, etc., the white blood cell count will gradually decrease and fever will appear. With effective antiviral treatment, the white blood cell count will gradually return to normal.2. Elderly people with low immunity may also have lowered white blood cell counts after combining with bacterial infections, especially negative bacillus infections, such as Pseudomonas aeruginosa, and the white blood cell count will gradually return to normal and the body temperature will return to normal after effective antibiotic treatment.3. Patients with previous illnesses with lowered white blood cell counts such as aplastic The patients have previous diseases with lowered white blood cells, such as aplastic anemia, malignant tumors of the blood system, radioactive work, long-term exposure to lead and mercury, as well as tumor patients after radiotherapy. If these patients have secondary bacterial or viral infections, high fever and lowered white blood cells will also occur.