Pediatric fever is one of the most common signs or symptoms in infants and children. Parents are anxious and nervous about this, especially, if it is the first time a baby has a fever. When a baby has a fever, the clinician will often recommend a routine blood test. Babies often have fever, parents will not understand the question —– just checked last time, why check again? Most babies with fever are colds, also known as “upper whistle infection”, more than 90% of the pathogens are viruses, which are treated without antibiotics. Another 10% or so are bacterial or other causes (including Mycoplasma pneumoniae). The identification is done by: blood tests and CRP (C-reactive protein – an indicator of inflammation, mostly bacterial infections when elevated: rheumatism, rheumatoid, tumors, etc. can also be elevated) monitoring. After the test, the baby can be given reasonable medication according to the situation. Avoid unreasonable use of antibiotics. If the white blood cells are around 10,000, or within 10,000, not less than 5,000, neutrophils are not high, generally only antiviral drugs and antipyretic drugs can be used, if 15,000 or so, neutrophils are also high, generally need to add antibacterial drugs, if the resistance is low, or often infusion, or white blood cells higher than 15,000, generally recommended infusion up, the use of antibacterial drugs.