dengue fever登革热

1、Dengue fever,Zhao zhixin The 3rd affiliated hospital of Sun Yat-Sen University ,WHAT IS DENGUE FEVER?,An acute ,self-limited, febrile disease . Dengue virus are maintained in a cycle that involves humans and Aedes aegypti primarily a disease of the tropics OCCURS IN two forms: Dengue fever(DF) Dengue haemorrhagic fever(DHF),Clinical manifestations,DF: fever, headache, myalgias, bone pain.Lymphadenopathy, skin rash. Leukopenia DHF: high fever, haemorrhage, hepatomegaly evidences of “leaky capilla

2、ries” signs of circulatory failure(dengue shock syndrome,DSS.),Why should we learn it ?,2500 million at risk from dengue per year. Epidemic in more than 100 countries in Africa, America, Eastern Mediterranean, South east Asia and the Western pacific. The global prevalence of DHF grown dramatically in recent decades: 1970/1995:4 fold increase. The most important mosquito-transmitted viral disease in term of mortality and morbidity.,Etiology,Dengue virus: enveloped RNA virus Classified : family of

3、 Flaviviridae. Serum type:1-4 causes closely related illness, severe and fatal disease but antigenically distinct homotypic immunity: lifelong heterotypic immunity :short period but cross-response may worsen the second infection by a another serum type.,How DF transmitted?,Sources of infection: patients and anyone who with Covert infection Transmitted vectors: Aedes aegypti is the most common vectors other Aedes mosquitos are less effiecitent : Ae.albopictus,Ae.polynesiesis Primarily a daytime f

4、eeder Lives around human habitation The host: all susceptible if never came across dengue fever.,How dengue virus cause the disease? (pathogenesis and clinical presentations),Dengue virus,Blood stream,Mononuclear-phagocyte system,second viremia,Antigen antibody complexes,complement system,incubation,Lymphadenopathy,hepatomegly,Bone marrow depress,Vascular permeability,Rash, haemarrhagic,fever Bone pains,etc,Imfllamatory materials,risk factors for DHF,Important risk factors for DHF include Virus

5、factors: the serotype :2 is the predominating the strain: virulent strain Host factors: genetic predisposition the age Children : experienced a precious dengue infection Infants with waning levels of maternal dengue antibody. immune status: if there are enhancing Ab.,Enchancing antibody,A mechanism of DHF/DSS is heterotypic antibodies enhancement of virus replication in macrophages worsen the condition,Neutralizing antibody to Dengue 1 virus,Dengue 1 virus,Homologous Antibodies(同型抗体) Form Non-in

6、fectious Complexes,Non-neutralizing antibody,Complex formed by neutralizing antibody and virus,Heterologous (异型的)Complexes Enter More Monocytes, Where Virus Replicates,Non-neutralizing antibody,Dengue 2 virus,Complex formed by non-neutralizing antibody and Dengue 2 virus,First infection,heterotypic antibodies,fail to neutralize virus of the other serum type infection,the number of infected monocytes,activation of cytotoxic lymphocytes,rapid release of cytokines,plasma leakage,viral uptake and th

7、e replication in the mononuclear phagocytes.,haemorrhage,Haemoconcentrationor shock,pathophysiological changes occur in DHF/DSS:,Increased vascular permeability haemoconcentration(Hct20%) low pulse pressure other signs of shock. Disorder in haemostaisis : vascular changes thrombocytopenia coagulopathy.,CLINICAL PRESENTATIONS,Incubation: 5-8 days Clinical features depend on the age of the patient: Infants and young children undifferentiated febrile disease, with maculapapular rash. Older children

8、 and adults either a mild febrile syndrome or the classic disease.,Manifestation Of Dengue Virus Infections,Undifferentiated Fever,the most common manifestation of dengue 87% of students infected were either asymptomatic or mildly symptomatic studies including all age- groups also demonstrate silent transmission,Dengue fever (DF),1. fever,Abrupt onset, rising to 39.5-41.4 C Accompanied by frontal or retro-orbital headache Pain behind the eyes chillness Last 1-7 days Biphasic: defervesce for 1-2

9、days recurring with second rash but :T not as high,2. Bone pains,break bone fever is the another name of DF After onset of fever May last several weeks Increase in severity Most common in legs, joints, and lumbar spine; With muscular and joint pains.,3. Rash,first rash: first 1-2 days of fever, transient, generalized, macular and blanching; Second rash 3-6 days. morbilliforms , maculopapular , rubella type Involving the trunk first, spreading to the face and extremities, sparing palms and soles. other rash: petechiae,4. Hemorrhage,Skin hemorrhages: petechiae, purpura Gingival bleeding Nasal bleeding GI bleeding: hematemesis, melena, hematochezia Hematuria Increased menstrual flow,Physical exams(1),Fever Conjunctival injection, pharyngeal erythema Rash: Measles-like rash over chest and upper limbs Generalized lymphadenopathy,Physical exams(2) : Tourniquet Test,Method: Inflate blood pres

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