Neutrophils are a type of white blood cell and both play an important role in fighting off infections from foreign pathogens. High leukocytes and neutrophils are most often seen in bacterial infections and, in rare cases, in viral infections. Spirochete infections can also cause increased leukocytes and neutrophils.1. Bacterial infections: Increased leukocytes and neutrophils are most commonly caused by bacterial infections, such as bacterial infections causing pneumonia, acute purulent tonsillitis, bacterial dysentery, acute gastroenteritis, and acute purulent appendicitis. In general, the more severe the infection, the higher the white blood cells and neutrophils. However, there are exceptions. In a small number of patients, the infection is very serious, but the leukocytes and neutrophils fall instead; 2. Viral infections: encephalitis caused by encephalitis B virus, renal syndrome hemorrhagic fever caused by hantavirus may show increased leukocytes and neutrophils early in the course of the disease; 3. Spirochete infections: for example, leptospirosis caused by Leptospira, syphilis caused by Lyme disease caused by Burkholderia spirochetes, and regressive fever caused by regressive fever spirochetes, manifesting as elevated leukocytes and neutrophils. In addition to the above mentioned infectious factors, there are also non-infectious factors, such as trauma to the body, acute poisoning, and hematologic lesions. There are many causes of elevated leukocytes and neutrophils. Patients are advised to visit the hospital promptly to clarify the cause and then take targeted treatment measures.