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Respiratory syncytial  virus
 

Respiratory syncytial virus

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Respiratory syncytial virus

Respiratory syncytial virus

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    Respiratory syncytial  virus Respiratory syncytial virus Presentation Transcript

    • RESPIRATORY SYNCYTIAL VIRUS Dr.T.V.Rao MDDR.T.V.RAO MD 1
    • DISCOVERY OF RESPIRATORY SYNCYTIAL VIRUS• In 1956, Morris and colleagues initially isolated RSV from chimpanzees with upper respiratory tract (URT) infections as the causative agent of most epidemic Bronchiolitis cases. Subsequently, Channock et al associated this agent with Bronchiolitis and LRT infection in infantsDR.T.V.RAO MD 2
    • RESPIRATORY SYNCYTIAL VIRUS• Respiratory syncytial virus (RSV) is a leading cause of severe respiratory infection in infants and children. RSV is an RNA virus whose genome encodes 10 proteins. The G protein is responsible for viral attachment to cells whilst the F protein promotes syncytia formation. DR.T.V.RAO MD 3
    • DIFFERS FROM PARAMYXOVIRUS • Unlike Paramyxovirus it does not posses Haemagglutinnins activity. • Do not posses neuraminidase or hemolytic properties • The size of nucelocapsid diameter is less than Paramyxovirus. • RS virus are placed in a separate Genus Pneumovirus DR.T.V.RAO MD 4
    • SERO TYPING OF RESPIRATORY SYNCYTIAL VIRUS• For all practical purposes there is only one serotype• With the use of monoclonal antibodies that there are two subtypes A and B strains. . DR.T.V.RAO MD 5
    • RSV FACTS • Most common cause of bronchiolitis & pneumonia in children under 1 • 25-40% of children develop bronchiolitis or pneumonia during first RSV infection • 31/1,000 under 1 yr. are hospitalized with RSV • 2% will dieDR.T.V.RAO MD 6
    • INFECTS ANIMALS TOO • RS virus infects cattle and chimpanzees • Both goats and sheep may be infected naturally • Even rodents can be adopted after some adoption. DR.T.V.RAO MD 7
    • RS VIRUS MAJOR CAUSE OF RESPIRATORY INFECTIONS.• Human respiratory Syncytial virus (RSV) was quickly determined to be of human origin and was shown to be the leading worldwide viral agent of serious paediatric respiratory tract disease. DR.T.V.RAO MD 8
    • RESPIRATORY SYNCYTIAL VIRUS (RSV) • ssRNA enveloped virus. • belong to the genus Pneumovirus of the Paramyxovirus family. • Considerable strain variation exists, may be classified into subgroups A and B by monoclonal sera. • Both subgroups circulate in the community at any one time. • Causes a sizable epidemic each year.DR.T.V.RAO MD 9
    • PATHOPHYSIOLOGY• Negative-strand RNA virus• Family Paramyxoviridae• RSV season late fall to early spring• Peak in January/February• Incubation 4-5 days, LRI between days 5-7DR.T.V.RAO MD 10
    • PROPAGATION OF RSV • It can be propagated in He La and Hep-2 cell culture lines. • Highly labile virus and promptly inactivated at room temperatures DR.T.V.RAO MD 11
    • MAJORITY OF CHILDREN ARE INFECTED • Almost all children will be infected with RSV by their second birthday. • RSV causes respiratory illness in infants and young children, and is the most important cause DR.T.V.RAO MD of Bronchiolitis. 12
    • PRESENTATION• Cold-like sx• Audible wheezing• SOB• Anorexia• Poor sleeping• Irritability• Vomiting• Choking DR.T.V.RAO MD 13
    • INVOLVEMENT OF ALVEOLI AND ALVEOLAR SPACE - A SIGNIFICANT FEATUREDR.T.V.RAO MD 14
    • MAJOR AREAS OF INFECTION IN RS VIRUSES• Clinical diagnosis will be supported with presence of RS virus in the Nasopharynx and there is clinical evidence of lower respiratory tract involvement. DR.T.V.RAO MD 15
    • IMMUNITY HELPS IN RECOVERY• The surface glycoproteins also evoke a host-derived antibody response following an infection. A primary RSV infection produces a weak humoral antibody response that does not differ with the severity of the disease. These responses are responsible for ending the infection and eliminating the virus, but do not appear to impart long-term immunity. In fact, it is only with reinfection that the antibody response is enhanced. If the infection reaches the LRT, a T cell- mediated response is generated.DR.T.V.RAO MD 16
    • CLINICAL FEATURES• The peak incidence is in those under 1 year of age.• The most serious illness manifest with Bronchiolitis in young babies• Leads to hyperinflation of lungs secondary to bronchiolar inflammation acting as a on way valve. DR.T.V.RAO MD 17
    • PATIENTS WITH RESPIRATORY SYNCYTIAL VIRUS (RSV) MAY PRESENT WITH THE FOLLOWING SYMPTOMS:• Fever (typically low- grade)• Cough• Tachypnea• Cyanosis• Retractions• Wheezing• Rales DR.T.V.RAO MD 18
    • SEVERITY OF RSV INFECTION IS DETERMINED BY:• Inhibition of certain interferons• Involvement of innate immune system• Interleukins and chemokines• Coinfection with other respiratory virusesDR.T.V.RAO MD 19
    • INHIBITION OF INTERFERONS• Interferons believed to have antiviral properties• NS1 & NS2 inhibit IFN-alpha/beta• Inhibition of IFN- gamma causes enhanced IgE productionDR.T.V.RAO MD 20
    • CAN BE LIFE THREATENING • The RS viral infection is potentially in those with or congenital heart disease Bronchopulmonary dysplasia defects, or in those who are Immunosupressed or Immunodeficient. DR.T.V.RAO MD 21
    • SUDDEN INFANT DEATH SYNDROME ( SIDS )• RS virus has been recovered from some victims of the Sudden infant death syndrome• Although it may have been contributed to death, other factor are also significantly contributed. DR.T.V.RAO MD 22
    • ACTIVE CLINICAL MANIFESTATIONS• The majority of infected present with clinical features of Bronchiolitis• In majority of cases recovery is complete.• In older children, and adults the virus cause minor illness,• Reinfections are common and in adults may cause no more than coldDR.T.V.RAO MD 23
    • RS VIRUS INFECTIONS CAN PREDISPOSE TO…. Some reports suggest the infection can predispose to Chronic respiratory tract disease, Asthma,Bronchectasis etc Several studies in progress to prove the predisposition with RS virus DR.T.V.RAO MD 24
    • CO - INFECTION• Rhinovirus contributes to increased severity in children with bronchiolitis• Metapneumovirus (hMPV) enhances or mimics symptoms of RSV bronchiolitis• 70% were confected w/ hMPV & required admission to PICUDR.T.V.RAO MD 25
    • RS VIRUS CAN INFECT OLD AGED GROUPS• There are upcoming reports of severe illness with some fatalities in old people’s homes as well as in elderly living in a community• The under diagnosis can be attributed lack of confirming Virological diagnosis in adults and elderly.DR.T.V.RAO MD 26
    • MANY FACTORS HAVE BEEN ASSOCIATED WITH INCREASED RISK OF ACQUIRING RSV DISEASE,• Attending child care centers.• Older siblings in preschool or school• Exposure to environmental pollutants (eg, cigarette smoke)• Multiple birth sets (especially triplets or greater)• Minimal breastfeedingDR.T.V.RAO MD 27
    • OTHER CONTRIBUTING FACTORS IN RESPIRATORY SYNCYTIAL VIRUS INFECTION• Premature children , especially birth at less than 35 weeks gestation• Age younger than 3 months at time of infection• Chronic lung disease• Congenital heart disease• Toxic appearance at time of presentation• Respiratory rate more than 70 per minute in room air• Atelectasis and/or pneumonitis on chest radiography• Oxygen less than 95% on room air• Doctorrao’s ‘e’ learning series DR.T.V.RAO MD 28
    • RS VIRUS DO NOT WITHSTAND FREEZING • The virus is relatively fragile and may not survive even snap –freezing at -700c • Specimens for isolation should not be frozen DR.T.V.RAO MD 29
    • RAPID DIAGNOSIS IN RS VIRAL INFECTIONS • In acute phase of illness, a Rapid diagnosis in > than 1 hour by Immunofluorescence with conjugated monoclonal antibodies with adequate number of desquamated respiratory cell is reliable. • However antigen detection and culture methods are good for diagnosing RS virus infection in infants and young children. DR.T.V.RAO MD 30
    • SEROLOGY• Serological assessment using complement fixation is generally not helpful.• Immunoassays for G and F proteins may offer more reliable serological tests, in adults where other options are limited. DR.T.V.RAO MD 31
    • MOLECULAR METHODS IN RESPIRATORY SYNCYTIAL VIRAL DETECTION• The emerging molecular methods such as reverse transcription- polymerase chain reaction, either for a single virus or multiplexed to detect a panel of viruses DR.T.V.RAO MD 32
    • TREATMENT• A supportive management with tube feeding in cases of difficulty in suckling• Use of oxygen if indicated.• Ribavirin is a specific antiviral drug, proved to effective when given as a small particle aerosol although it is apparently not effective intravenous infusion.DR.T.V.RAO MD 33
    • INDICATION FOR CHEMOTHERAPY• The chemotherapy with Ribavirin is expensive and its recommended use is confined to those babies who are at risk from rampant RS virus, because they have congenital heart or lung abnormalities• The use os Hyper immune RS virus immunoglobulin and humanized monoclonal antibodies have become available for treatment and prevention of RS infection. In view of higher costs they are warranted in selected infants born with low birth weight or preexisting Bronchopulmonary dysplasiaDR.T.V.RAO MD 34
    • SUPPORTING TREATMENT• Mostly symptomatic• Salbutamol MDI drug of choice• Also use epinephrine, ipratropium bromide, & oral steroids only if hospitalizedDR.T.V.RAO MD 35
    • EPIDEMICS AND SEASONAL VARIATION• In temperate climates in both the northern and southern hemisphere, RS virus causes a substantial winter epidemic every year.• In tropical regions the epidemics manifest in hot periods of summer.• However sporadic cases occur throughout the year• The RS virus produces infections all over the world DR.T.V.RAO MD 36
    • MORBIDITY & MORTALITY• More likely to suffer recurrent infections• Many have recurrent acute otitis media• Many likely to be hospitalized with another episode of acute respiratory distressDR.T.V.RAO MD 37
    • MORBIDITY & MORTALITY• Adolescents suffer from allergic asthma, allergic rhino conjunctivitis, & more sensitive to inhaled allergens• More likely to have asthma, bronchial reactivity to methacholine, and reduced lung function• RSV ind. risk factor for reduced FEV% (FEV1/FVC)DR.T.V.RAO MD 38
    • ENVIRONMENTAL & DEMOGRAPHICS• Male infants• Age & birth month of infant• Crowding & day care attendance• Secondhand smokeDR.T.V.RAO MD 39
    • VACCINE - FAILURES • A formalin inactivated crude, whole virus vaccine was tried in 1960, but failed to produce immunity in the recipients • The difficulties in preparing safe vaccine for RSV lie with young and immunologically immature recipients. • Yet to date there is no safe vaccine available for universal use DR.T.V.RAO MD 40
    • FOR ARTICLES OF CURRENT INTEREST ON INFECTIOUS DISEASES FOLLOW ME ON..DR.T.V.RAO MD 41
    • • Created by Dr.T.V.Rao MD for ‘e’ learning resources for Microbiologists in Developing World • Email • doctortvrao@gmail.comDR.T.V.RAO MD 42