Dengue fever (dengue) is an acute insect-borne infectious disease caused by dengue virus transmitted by mosquito vector. Dengue virus infection can lead to occult infection, dengue fever, dengue hemorrhagic fever, dengue hemorrhagic fever is rare in China. Typical clinical manifestations of dengue fever are rapid onset, high fever, headache, severe muscle and bone and joint pain, rash, bleeding tendency, lymph node enlargement, reduced white blood cell count and thrombocytopenia in some patients. The disease is mainly prevalent in tropical and subtropical areas, and Guangdong, Hong Kong and Macau are the endemic areas of dengue fever in China. Since the disease is transmitted by Aedes aegypti mosquito, so the epidemic has a certain seasonality, generally in May to November each year, with a peak in July to September. In the new epidemic area, the population is generally susceptible, but the onset of the disease is mainly in adults, and in the endemic area, the onset of the disease is mainly in children. During the romantic summer months, it can sometimes be very troublesome to be bitten by the “slender mouth” of a certain insect. A can spread a variety of insect-borne diseases of mosquitoes, some people are bitten after the possibility of certain insect-borne diseases, sometimes causing the next generation of deformities, and can even cause death. For clinicians how do we diagnose dengue fever I. Diagnostic principles According to the epidemiological history of the patient, clinical manifestations and laboratory test results for a comprehensive judgment. Case definition 1. Suspected case is a suspected case if one of the following conditions is met: (1) Epidemiological history (visited dengue endemic area within 14 days before the onset), with acute onset, fever (39oC~40oC within 24h~36h, a few are bimodal fever), more intense headache, orbital pain, general muscle pain, bone and joint pain and obvious fatigue and other general clinical symptoms. It may be accompanied by flushing of the face, neck and chest, and conjunctival congestion. (2) No epidemiological history, but with both the above general clinical symptoms and the following symptoms: (1) Rash: It appears on the 5th to 7th day of the course of the disease and is a diverse rash (measles-like rash, scarlet fever-like rash, acne-like hemorrhagic rash) or “skin island”-like manifestation. The rash is distributed on the trunk of the extremities or on the head and face, and is mostly itchy and non-flaky. It lasts for 3 to 5 days. (2) Bleeding tendency (positive arm-binding test): petechiae, petechiae, purpura and injection site bleeding, gum bleeding, nasal bleeding and other mucosal bleeding, gastrointestinal bleeding, hemoptysis, hematuria, vaginal bleeding, etc. generally appear on the 5th to 8th day of the course of the disease. 2. Clinical diagnosis of cases (1) Typical dengue fever can be diagnosed by meeting one of the following conditions: 1) general clinical symptoms of dengue fever and epidemiological history, i.e. having been to a dengue fever endemic area within 14 days before the onset of the disease, or having a case of dengue fever within 1 month around the residence or workplace, and having a reduced white blood cell count and thrombocytopenia (less than 100×109/L). (2) Those who have no epidemiological history but have rash, bleeding tendency, and positive single copy of serum specific IgG antibody or IgM antibody. (2) Dengue hemorrhagic fever (DHF) Typical dengue fever with one of the following clinical symptoms: bleeding tendency, obvious bleeding manifestations (gastrointestinal hemorrhage, or thoracoabdominal or intracranial hemorrhage), hepatomegaly, thoracoabdominal effusion; and laboratory tests show thrombocytopenia (less than 100×109/L), hematoconcentration (hematocrit increased by more than 20% compared with normal level, or hematocrit decreased by 20% compared with baseline level after volume expansion treatment). (or the hematocrit decreases by more than 20% from the baseline level after volume expansion treatment) and hypoalbuminemia. (3) Dengue shock syndrome (DSS) Patients with dengue hemorrhagic fever present with wet and cold skin, irritability, fine pulse, hypotension, pulse pressure less than 20 mmHg (2.7 kPa), undetectable blood pressure, decreased urine output and other shock manifestations. (1) Dengue virus is isolated from the serum, cerebrospinal fluid, blood cells or tissues of patients in the acute stage. (2) The dengue virus gene sequence is detected by RT-PCR or real-time fluorescence quantitative PCR. (3) Dengue virus NS1 antigen was detected in the serum of patients in the acute phase (4) There was a 4-fold or more increase in serum-specific antibody titers in the recovery phase compared with the acute phase.