When a young child has a low fever that does not go away, the first thing that should be ruled out is a low fever caused by a chronic infection. When a chronic infection occurs, the fever is often less severe and will show up as a low fever because the symptoms of the infection have not resolved, so the temperature does not return to normal, so the low fever does not go away. At this time, blood cultures, routine blood tests, and C-reactive protein tests can be done to determine the cause, such as the presence of elevated white blood cells, which in many cases is the occurrence of a chronic bacterial infection. If there is a simple elevation of C-reactive protein, it is likely that a chronic viral infection has caused the fever to go away. If the C-reactive protein and blood count are not abnormal, it is important to take the child to the hospital for a specific examination to clarify the cause of the fever. Because of the presence of hypothermia, it does not exclude hypothermia caused by rheumatic immune system diseases, such as systemic lupus erythematosus. Although tumors are relatively rare, they also need to be taken seriously and cannot be ruled out.