Asymptomatic fever of 39 degrees is usually related to the presence of infection in the organism. In addition, autoimmune diseases, hematological diseases, tumor diseases, etc., may also affect the normal heat production and heat dissipation, resulting in asymptomatic fever of 39 degrees, it is recommended to seek medical attention in a timely manner to avoid delaying the disease. 1. Infectious diseases: If the body’s resistance is poor, after cold or exertion, it is easy to induce infection and develop a body temperature of 39 degrees but no cough , nasal congestion and other symptoms. The fever can be reduced by using acetaminophen tablets, lysergic acid and other drugs under the guidance of a doctor. 2. Autoimmune diseases: such as systemic lupus erythematosus and autoimmune thrombocytopenia may affect the normal function of the thermoregulatory center and cause an asymptomatic fever of 39 degrees during an acute attack of the disease. 3. Hematological diseases: such as myelodysplasia and leukemia, which may also manifest as asymptomatic Fever 39 degrees, can improve blood routine, bone marrow aspiration biopsy and other examinations to clarify the cause, and actively follow medical advice for treatment; 4, tumor diseases: such as lung cancer, gastric cancer and other tumor diseases, when tumor cell destruction release tumor factors can cause tumor fever, manifested as asymptomatic fever 39 degrees, can be clearly diagnosed through CT, X-ray and other examinations; 5, other: recent improper food, poor medication and other serious allergies If you have been in a high temperature environment for a long time and have heatstroke, you may also have asymptomatic fever of 39 degrees and your body temperature is not lowered, you should seek medical treatment in time.