Frequent fever in the elderly may be due to the following reasons. 1. Elderly people often have colds due to low immune function, especially during the change of seasons, which often leads to fever. 2. Elderly patients with tuberculosis have low fever in the afternoon as the main clinical manifestation, especially in the early stage of the disease when the symptoms are not typical and often not easy to detect. 3. Elderly patients with tumors may also have moderate to high fever, which is caused by the absorption of tumor necrosis. 4. 4. Rheumatic immune system diseases, such as rheumatism and rheumatoid arthritis, can also lead to fever in the elderly. 5. Hematologic diseases, such as leukemia and myelodysplastic syndrome, are also common causes of fever in the elderly. In addition, elderly patients with HIV infection may also experience recurrent fever.