High fever of bacterial infection in 40-day-old infants can be seen in intracranial infections, respiratory diseases and other conditions, the treatment needs to be carried out according to the cause of the disease, such as intracranial infections need to be actively anti-infective, lowering the cranial pressure and other treatments as appropriate. 1. Intracranial infection: it can be caused by bacterial infection, such as meningococcus, etc. Clinical recurrence of fever can occur, may present high fever, body temperature over 39.0 ℃, may be accompanied by convulsions, poor response and other symptoms, perfect lumbar puncture examination can be seen in the leukocyte increase, part of the cerebrospinal fluid culture can be seen in the causative organisms positive. Treatment requires active use of antibacterial drugs (such as ceftazidime, etc.) to actively fight infection, and the use of mannitol and other appropriate treatment to reduce cranial pressure. For this age group of babies, there is no safe antipyretic drugs for symptomatic antipyretic, you can use warm water wiping and other ways of physical cooling, to be controlled by the disease, fever can be gradually relieved. 2. respiratory system diseases: such as acute upper respiratory tract infection, can be secondary to bacterial infection, clinical phenomenon of high fever, such babies need to actively use antimicrobial drugs (such as cefaclor) anti-infective treatment, the course of physical cooling, and need to closely observe the mental and other conditions. 3. Infectious diarrhea: can be caused by Escherichia coli and other causes, clinical phenomena can occur, accompanied by vomiting, diarrhea and other symptoms, routine stool examination can be seen obvious leukocytes, the treatment requires the use of antibacterial drugs (such as cefotaxime) anti-infective and physical cooling and other treatments, if necessary, need to replenish the water electrolytes to prevent or correct dehydration and other treatments. All of the above drugs should be used under the guidance of a physician, and it is recommended to actively seek medical advice from a specialist to assess the condition and guide the treatment.