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Respiratory Syncitical Virus


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Respiratory Syncitical Virus

  1. 1. Respiratory Syncytial Virus infections Dr.T.V.Rao MD
  2. 2. Discovery of Respiratory Syncytial Virus <ul><li>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 infants. Since then, multiple epidemiologic studies have confirmed the role of this virus as the leading cause of LRT infection in infants and young children. </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  3. 3. RS virus major cause of Respiratory Infections. <ul><li>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 . </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  4. 4. RSV – Viral structure <ul><li>RSV is Plemomorphic and ranges in size from 150 – 300nm </li></ul><ul><li>The viral envelope has two glycoprotein's- the G protein by which the virus attaches to cell surfaces, and fusion (F) protein which brings about fusion between viral and host cell membranes. </li></ul><ul><li>The F protein is also responsible for cell to cell fusion, which is responsible for typical syncytial cytopathic changes in RSV infection. </li></ul>
  5. 5. Respiratory Syncytial virus <ul><li>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. </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  6. 6. Differs from Paramyxoviruses <ul><li>Unlike Paramyxoviruses it does not posses Haemagglutinnin activity. </li></ul><ul><li>Do not posses neuraminidase or hemolytic properties </li></ul><ul><li>The size of nucelocapsid diameter is less than Paramyxoviruses. </li></ul><ul><li>RS virus are placed in a separate Genus Pneumovirus </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  7. 7. RS virus do not withstand freezing <ul><li>The virus is relatively fragile and may not survive even snap –freezing at -70 0 c </li></ul><ul><li>Specimens for isolation should not be frozen </li></ul>
  8. 8. Propagation of RSV <ul><li>It can be propagated in He La and Hep-2 cell culture lines. </li></ul><ul><li>Highly labile virus and promptly inactivated at room temperatures </li></ul>
  9. 9. Sero typing of Respiratory Syncytial virus <ul><li>For all practical purposes there is only one serotype </li></ul><ul><li>With the use of monoclonal antibodies that there are two subtypes A and B strains . </li></ul><ul><li>In Newcastle upon Tyne, strains of subtype A have been prevalent every year since 1974 </li></ul><ul><li>But subgroup B strains were erratic and have not been isolated every winter. </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  10. 10. Infects Animals too <ul><li>RS virus infects cattle and chimpanzees </li></ul><ul><li>Both goats and sheep may be infected naturally </li></ul><ul><li>Even rodents can be adopted after some adoption. </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  11. 11. Majority of Children are Infected <ul><li>Almost all children will be infected with RSV by their second birthday. </li></ul><ul><li>RSV causes respiratory illness in infants and young children, and is the most important cause of Bronchiolitis. </li></ul>
  12. 12. RS virus is major cause of Respiratory Infection - Globally <ul><li>Respiratory Syncytial virus (RSV) is recognized as the most important cause of serious lower respiratory tract illness in infants and young children worldwide causing repeat infections throughout life with serious complications occurring in the elderly and immune compromised patient. </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  13. 13. Involvement of Alveoli and Alveolar space - A significant feature
  14. 14. Major areas of Infection in RS viruses <ul><li>Clinical diagnosis will be supported with presence of RS virus in the Nasopharynx and there is clinical evidence of lower respiratory tract involvement. </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  15. 15. Clinical Features <ul><li>The peak incidence is in those under 1 year of age. </li></ul><ul><li>The most serious illness manifest with Bronchiolitis in young babies </li></ul><ul><li>Leads to hyperinflation of lungs secondary to bronchiolar inflamation acting as a on way valve. </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  16. 16. Patients with respiratory syncytial virus (RSV) may present with the following Symptoms : <ul><li>Fever (typically low-grade) </li></ul><ul><li>Cough </li></ul><ul><li>Tachypnea </li></ul><ul><li>Cyanosis </li></ul><ul><li>Retractions </li></ul><ul><li>Wheezing </li></ul><ul><li>Rales </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  17. 17. Can be Life Threatening <ul><li>The RS viral infection is potentially in those with or congenital heart disease Bronchopulmonary dysplasia defects, or in those who are Immunosupressed or Immunodeficient. </li></ul>
  18. 18. Sudden Infant Death syndrome ( SIDS ) <ul><li>RS virus has been recovered from some victims of the Sudden infant death syndrome </li></ul><ul><li>Although it may have been contributed to death, other factor are also significantly contributed. </li></ul>
  19. 19. Active Clinical manifestations <ul><li>The majority of infected present with clinical features of Bronchiolitis </li></ul><ul><li>In majority of cases recovery is complete. </li></ul><ul><li>In older children, and adults the virus cause minor illness, </li></ul><ul><li>Reinfections are common and in adults may cause no more than cold . </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  20. 20. RS virus infections can predispose to…. <ul><li>Some reports suggest the infection can predispose to Chronic respiratory tract disease, Asthma,Bronchectasis etc </li></ul><ul><li>Several studies in progress to prove the predisposition with RS virus </li></ul>
  21. 21. RS virus can infect old aged groups <ul><li>There are upcoming reports of severe illness with some fatalities in old people’s homes as well as in elderly living in a community </li></ul><ul><li>The under diagnosis can be attributed lack of confirming Virological diagnosis in adults and elderly. </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  22. 22. Factors have been associated with increased risk of acquiring RSV disease, <ul><li>Attending child care centres. </li></ul><ul><li>Older siblings in preschool or school </li></ul><ul><li>Exposure to environmental pollutants (eg, cigarette smoke) </li></ul><ul><li>Multiple birth sets (especially triplets or greater) </li></ul><ul><li>Minimal breastfeeding </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  23. 23. Other contributing factors in Respiratory syncitical virus Infection <ul><li>Premature children , especially birth at less than 35 weeks' gestation </li></ul><ul><li>Age younger than 3 months at time of infection </li></ul><ul><li>Chronic lung disease </li></ul><ul><li>Congenital heart disease </li></ul><ul><li>Toxic appearance at time of presentation </li></ul><ul><li>Respiratory rate more than 70 per minute in room air </li></ul><ul><li>Atelectasis and/or pneumonitis on chest radiography </li></ul><ul><li>Oxygen less than 95% on room air </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  24. 24. Laboratory Diagnosis of RS viral infection . <ul><li>Viral detection and Isolation </li></ul><ul><li>In acute phase virus may be demonostrated by Immunofluorescence, Enzyme immuno assays and Culture </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  25. 25. Rapid Diagnosis in RS Viral infections <ul><li>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. </li></ul><ul><li>However antigen detection and culture methods are good for diagnosing RS virus infection in infants and young children. </li></ul>
  26. 26. Serology <ul><li>Serological assessment using complement fixation is generally not helpful. </li></ul><ul><li>Immunoassays for G and F proteins may offer more reliable serological tests, in adults where other options are limited. </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  27. 27. Molecular Methods in RS viral infection <ul><li>The emerging molecular methods such as reverse transcription-polymerase chain reaction, either for a single virus or multiplexed to detect a panel of viruses </li></ul>
  28. 28. Treatment <ul><li>A supportive management with tube feeding in cases of difficulty in suckling </li></ul><ul><li>Use of oxygen if indicated. </li></ul><ul><li>Ribavirin is a specific antiviral drug, proved to effective when given as a small particle aerosol although it is apparently not effective intravenous infusion. </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  29. 29. Indication for Chemotherapy <ul><li>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 </li></ul><ul><li>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 dysplasia </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  30. 30. Epidemics and Seasonal Variation <ul><li>In temperate climates in both the northern and southern hemisphere, RS virus causes a substantial winter epidemic every year. </li></ul><ul><li>In tropical regions the epidemics manifest in hot periods of summer. </li></ul><ul><li>However sporadic cases occur throughout the year </li></ul><ul><li>The RS virus produces infections all over the world </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  31. 31. Vaccine - Failures <ul><li>A formalin inactivated crude, whole virus vaccine was tried in 1960, but failed to produce immunity in the recipients </li></ul><ul><li>The difficulties in preparing safe vaccine for RSV lie with young and immunologically immature recipients. </li></ul><ul><li>Yet to date there is safe vaccine avialble for universal use </li></ul><ul><li>Doctorrao’s ‘e’ learning series </li></ul>
  32. 32. Created for awarness on Respiratory Syncytial Viral Infections in Developing world Dr.T.V.Rao MD Email [email_address]