Fever without cold symptoms may be associated with infectious diseases such as upper respiratory tract infections, pneumonia and bronchitis, urinary tract infections, etc., as well as non-infectious diseases such as oncologic diseases, endocrine and rheumatic diseases. 1. Infectious diseases: (1) Upper respiratory tract infection: fever without cold symptoms may be that the symptoms of respiratory tract infection have not been fully manifested, and fever is the first symptom to appear. At this time, it is necessary to continue to observe, if the later appearance of nasal congestion, runny nose, cough, cough sputum and other symptoms, may be mostly upper respiratory tract infection caused by fever. (2) Pneumonia and bronchitis: this type of disease may not have symptoms such as colds at the beginning, but will cause fever due to the inflammatory reaction. (3) Urinary tract infection: For example, in acute pyelonephritis, there will be fever, frequent urination, urgency and pain of urination without symptoms of cold. 2. Non-infectious diseases: (1) Tumor diseases: for example, when leukemia, malignant lymphoma and other diseases are in advanced stage, tumor cells will produce pyrogen causing fever. Usually, the temperature of tumor fever is not too high, which is about 38℃. (2) Endocrine diseases: such as hyperthyroidism, due to the increase of body heat production caused by thyroid hormone, low fever symptoms may occur. (3) Rheumatic immune diseases: such as vasculitis, systemic lupus erythematosus, etc., fever symptoms can also occur. Fever without cold symptoms can also be seen in a variety of other diseases, you should seek medical attention as soon as possible to identify the cause of the disease, to avoid misjudgment of the cause of fever.