2019年江苏省疟疾防治工作检查29.ppt

Influenza:epidemiology,prevention and controlTom D.Y.Chin,MD.MPHDepartment of Preventive Medicine and of MedicineUniversity of Kansas Medical CenterImportance of InfluenzaOne of the most important Emerging and Reemerging infectious diseases Causes high morbidity and mortality in communities(epidemic)and worldwide(pandemic)Epidemics are associated with excess mortalityLeading Causes of Deaths in the USHeart DiseaseCancerCVDChr Obst Lung DisAccidentsPneumonia&InfluenzaDiabetes MellitusHIVSuicideHomicideLeading Causes of Deaths in the USHeart DiseaseCancerCVDChr Obst Lung DisAccidentsPneumonia&InfluenzaDiabetes MellitusHIVSuicideHomicideCharacteristics of Influenza VirusTypes A,B,CDiameter 80-120 nmPleomorphic,spherical,filamentous particlesSingle-stranded RNASegmented genome,8 segments in A and BHemagglutinin and Neuraminidase on surface of virionCausative Agent of InfluenzaCaused by a virus belonging to the MYXOVIRUS group which comprises of Orthomyxovirus and Paramyxovirus Influenza virus is an Orthomyxovirus Classification of Influenza virusClassified on the basis of hemagglutinin(HA)and neuraminidase(NA)15 subtypes of HA and 9 subtypes of NA are known to exist in animals(HA 1-15,NA 1-9)3 subtypes of HA(1-3)and 2 subtypes of NA(1-2)are human influenza viruses.HA 5,7,9 and NA 7 can also infect humansDiscovery of Influenza VirusFirst isolated from a pig in 1931(swine flu)Isolated from human in 1933Nomenclature of Human Influenza VirusMode of Transmission In HumanThe virus is spread from person-to-person through respiratory secretions either as droplets(close contact)or as airborne infection by droplet nuclei suspended in the air.Incubation period 1-3 daysClinical ManifestationsInfluenza is an acute respiratory illness characterized by fever,headache,myalgia,coryza,sore throat and cough.Cough is frequently severe and protracted.Duration of illness is usually 2-7 days.Clinical DiagnosisThe clinical picture of influenza is nonspecific.Influenza-like illness can be caused by many microbial agents other than influenzavirus,such as adenovirus,parainfluenza viruses,coronavirus,Mycoplasma pneumoniae,Chlamydia pneumoniae,beta-hemolytic streptococcus.Laboratory DiagnosisSince the clinical picture of influenza is nonspecific,its specific diagnosis must be confirmed by laboratory tests.This is usually made by virus isolation,identification of specific antigens or antibody rise.Antigenic VariationInfluenza viruses tend to undergo changes from time to time.There are two types of changes:(1)antigenic shift,(2)antigenic drift.These changes in the antigenic characteristics of influenza viruses determine the extent and severity of influenza epidemicsAntigenic ShiftThis term denotes MAJOR changes in hemagglutinin and neuraminidase resulting from reassortment of gene segments involving two different influenza viruses.When this occurs,worldwide epidemics may be the consequence since the entire population is susceptible to the virus.Pandemic Influenza VirusesAntigenic DriftThis term denotes MINOR changes in hemagglutinin and neuraminidase of influenza virus.This results from mutation in the RNA segments coding for either the HA or NAThis involves no change in serotype;there is merely an alteration in amino acid sequence of HA or NA leading to change in antigenicity.Influenza A(H3N2)VariantsA/Port Chalmer/73A/Victoria/3/75A/Texas/1/77A/Bangkok/79A/Philippines/2/82Influenza A Epidemic Excess Mortality,USDeath Rates of Persons with ARI during Influenza Epidemics,Houston,1978-1981Hospitalization Rates for ARI during Influenza Epidemic,Houston,1980-81Rates of Visits to Physicians for ARI during Influenza Epidemic,Houston,1983Reservoirs of Influenza VirusesAquatic birdsPigs HumansControl MeasuresImmunoprophylaxis with vaccineChemoprophylaxis and chemotherapyTypes of VaccineInactivated,consisting of(1)whole-virus,(2)subvirion,(3)purified surface antigen.Only subvirion or purified antigen should be used in children.Any of the three can be used for adults.Live attenuatedInfluenza Vaccine,who should receive itPersons 65 yrs or olderPersons with heart,pulmonary,renal and metabolic diseases.Persons in nursing homes and other long-term care facilitiesPersons 6 mos-18 yrs old receiving aspirin therapyInfluenza vaccine recipients-continuedWomen in 2nd or 3rd trimester of pregnancy during flu season.Household members of persons in high-risk groupsHealth care workers and others providing essential community services.Antiviral DrugsAmantadine,rimantadine.Effective for prevention and treatment of flu A only.Zanamivir,oseltamivir are approved for treatment of uncomplicated flu A&B;oseltamivir also approved for prophylaxis.Prophylaxis must be continued throughout the epidemic;treatment must begin within 24 hrs of onset of 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