Regression fever is an acute infectious disease caused by regression spirochetes transmitted by insect vectors, clinically characterized by periodic high fever with generalized pain, hepatosplenomegaly and hemorrhagic tendency, and jaundice in severe cases. According to the different vectors, it can be divided into two types: lice-borne regression fever (epidemic regression fever) and tick-borne regression fever (endemic regression fever). Most patients have an increased total white blood cell count of up to 1.5 to 2 x 1010/L and increased neutrophils. How to effectively prevent and treat regression fever? Tetracycline is the drug of choice for the treatment of the two types of return fever, the daily amount of adults is 1.5-2g, children 30-40mg/kg; 4 times divided dose, can’t be taken orally when switched to intravenous administration, adults should not be more than 1g per day. doxycycline, penicillin, etc. can also be used, the former amount of adults per day is 200mg, 2 times divided dose; the latter is 600,000-800,000U per day, divided into 2 times of intramuscular injection. Caution should be taken to prevent the shock reaction that occurs when the periplasm is killed and dissolved in large quantities. The course of treatment is 7-10d, and adrenocorticotropic hormone can be combined when there is severe toxemia or shock reaction. Treatment should be initiated early in the fever or during the fever-free period, but should not be given near the end of the attack because of the risk of the Jarisch-Herxheimer reaction, which is sometimes fatal in lice-borne regression fever. Personnel and equipment should be available to prevent this reaction. In tick-borne regression fever, acetaminophen 650 mg 2 hours before and 2 hours after the first dose of tetracycline or erythromycin may reduce the Jarisch-Herxheimer reaction. Symptomatic treatment should be given to anyone with high fever and severe illness. Dehydration and electrolyte imbalance should be corrected by fluids. Oral administration of 30-60 mg of codeine every 4 to 6 hours may be used to relieve severe headache. Nausea and vomiting can be treated with 50-100mg of tebuconazole (or 50mg intramuscularly) or 5-10mg of prochlorperazine orally or intramuscularly every 4 hours, 1-4 times daily. If heart failure occurs, special treatment should be given accordingly. During the period of fever, bed rest should be given, high-calorie diet, adequate amount of water and cooling, and symptomatic treatment such as adrenocorticotropic hormone should be used if necessary. Antibiotics can eliminate the spirochetes in the body, so the treatment has special effect, tetracycline antibiotics is currently the most effective drugs, generally choose tetracycline, benzylpenicillin, procaine penicillin efficacy is also good, foreign reports of the tonicity of 100mg of penicillin can also be a good effect. Slow absorption of penicillin can not kill the spirochetes in the brain, so the disease may recur after treatment; part of the tick-borne regression fever is not sensitive to penicillin, so it is not suitable for selection; antibiotic treatment must pay close attention to the possibility of serious shock reaction that Yarisch-Hexheimer’s reaction, and the heaviest can be fatal, which may be a large number of spirochetes dissolved in anaphylactic shock reaction, so the first dose of antibiotics should not be too Therefore, the first antibiotic dose should not be too large and can be combined with adrenocorticotropic hormone if necessary. Neoarspheniramine should only be used in patients with advanced recurrent tick-borne regurgitation fever that is poorly responding to antibiotics. The recurrence rate of tick-borne fever is 20% or higher with single-dose therapy because the spirochetes of tick-borne fever invade the brain more often, and the spirochetes are protected by the blood-brain barrier and remain in the brain, where they can re-invade the bloodstream as soon as the blood levels of antibiotics drop. Therefore, the treatment regimen of choice for adults: tetracycline at a dose of 500mg, or 12.5mg/kg body weight, 4 times/d, orally for 10 days. Or doxycycline 100mg 2x/d orally for 10 days. If tetracycline is contraindicated, erythromycin 500 mg, or 12.5 mg/kg body weight, 4 times/d, orally for 10 days. If CNS invasion is identified or suspected, intravenous penicillin G at 3 million U, 6 times/d, or ceftriaxone 2 g, intravenously, 1 time/d, or divided into 2 injections for 10 to 14 days is used. Early application of antibiotics is more effective. Children have a good prognosis, and the prognosis is worse for the old and weak and pregnant women. The prognosis for those with serious complications is dire. The mortality rate of tick-borne return fever is 2%～6%, and can be as high as 50% in pandemic. The mortality rate of tick-borne fever is 2% to 5%, but the mortality rate of newborns can be as high as 60%.