Regression fever is an acute infectious disease caused by insect-borne spirochetes, characterized by periodic high fever with generalized pain, hepatosplenomegaly and bleeding tendency, and jaundice in severe cases. Depending on the vector, the disease can be divided into two types: louse-borne regressive fever (epidemic regressive fever) and tick-borne regressive fever (endemic regressive fever). Most patients have an increased total white blood cell count, up to 1.5-2×1010/L, and increased neutrophils. 1, Platelets and clotting time are mostly normal, but severe cases may have abnormalities. 2.Serum alanine aminotransferase is often elevated, and serum bilirubin may be increased. 3.Small amount of protein, tubular type and red and white blood cells in urine. 4.Cerebrospinal fluid pressure is slightly increased, and protein and lymphocytes are mildly increased. 5.Spirochetes can be found in blood or bone marrow smear staining microscopy or dark field examination during the febrile period. The disease must be differentiated from typhus, typhoid fever, influenza, leptospirosis, epidemic hemorrhagic fever, septicemia, etc. before the return of the fever type. There is no vaccine for immunoprophylaxis, so the focus remains on cutting off the transmission route and controlling the source of infection. The prevention of louse-borne regressive fever should pay attention to isolation of patients and complete extermination of lice. Observation should be continued for 15 days after the fever has subsided. The contact person should also be thoroughly exterminated lice, if necessary, oral doxycycline 100mg to prevent the disease. Tick-borne regressive fever should be exterminated by ticks and rodents. The tick can be sprayed with malathion or dichlorvos, and the rodent can be poisoned with drugs and trapped and beaten. When performing tasks in infected areas should pay attention to personal protection, if necessary, oral doxycycline or tetracycline to prevent morbidity. Most patients have an increased total white blood cell count of 1.5 to 2×1010/L and increased neutrophils.