Fever should be the most common symptom! I’m sure everyone has been harassed by fever during their long journey through life. It’s no wonder that the first thing in an undergraduate medical diagnostics textbook is fever. However, the vast majority of fevers resolve themselves on the patient’s own – some subside on their own, some go to the pharmacy and buy some medicine and get better. Only a very small percentage of the persistent ones need to seek medical attention in a hospital and be dealt with by a physician. Don’t underestimate this small percentage of patients with fever! The true cause of all fevers cannot be determined by the current state of medical care. Note that this embarrassing situation is not a Chinese specialty, but a global problem. Some experts say that in developed countries in Europe and the United States, the percentage of fever investigations that do not clarify the cause of the disease is as high as 30%! I think it is a bit exaggerated, but 10% is still very likely. Therefore, any clinician who has a patient with fever in his hands is most likely to be in a state of anxiety. Many physicians would rather admit a patient with a clear etiology but in critical condition than take on a patient with a febrile cause finding. This is because the greatest fear is the unknown. There are so many diseases that can cause fever! And some of them are very insidious. In our department we had a young patient with a fever whose cause was unknown until his death. Although an autopsy after the fact clarified the diagnosis of lymphoma, there is no evidence of lymphoma that can be found until an autopsy is performed. Sometimes it takes not only a great deal of clinical experience but also a great deal of reading of the literature to find the real culprit. The workload of one patient is equivalent to more than three times that of a patient without fever! Therefore, patients and their families who are investigating the cause of fever in the hospital should not look at fever as simple as it is, and should not say things like “I can’t handle a single fever”, and should fully cooperate with the doctor in charge of their work. Only in this way can we hope to find the real cause.