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Lect 5 - Respiratory viruses

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Lect 5 - Respiratory viruses

  1. 1. Respiratory Viruses
  2. 2. Viruses Associated with Respiratory Infections Syndrome Commonly Associated Viruses Coryza Rhinoviruses, Coronaviruses Influenza Influenza viruses Croup Parainfluenza viruses Bronchiolitis RSV Bronchopneum onia Influenza virus, RSV, Adenoviruses
  3. 3. Influenza Virus  RNA virus  Enveloped virus, with haemagglutinin (HA) and neuraminidase (NA) spikes  3 types: A, B, and C  Type A undergoes antigenic shift and drift.  Type B undergoes antigenic drift only  Type C is relatively stable (Courtesy of Linda Stannard, University of Cape Town, S.A.)
  4. 4. Influenza A Virus  Antigenic shift is an abrupt change of the HA due to genetic reassortment: results in pandemics  Antigenic drift is a gradual change in the HA and NA proteins: results in epidemics
  5. 5. Reassortment Avian H3 Human H2 Human H3 Reassortment of the H and N genes between human and avian influenza viruses through a third host.
  6. 6. Epidemiology Epidemics  Epidemics of influenza A and B arise due to minor antigenic drifts as a result of mutation Pandemics  Due to antigenic shift a virus with a new haemagglutinin subtype emerges  The population has no immunity against the new strain  Three antigenic shifts occurred in the 20th century
  7. 7. Past Antigenic Shifts 1918 H1N1 “Spanish Influenza” 20-40 million deaths 1957 H2N2 “Asian Flu” 1-2 million deaths 1968 H3N2 “Hong Kong Flu” 700,000 deaths 1977 H1N1 Re-emergence No pandemic At least 15 HA subtypes and 9 NA subtypes occur in nature. Up until 1997, only viruses of H1, H2, and H3 are known to infect and cause disease in humans.
  8. 8. Influenza Virus Replication
  9. 9. Avian Influenza H5N1  An outbreak of Avian Influenza H5N1 in Hong Kong in 1997  The source of the virus was probably infected chickens  Was controlled by a mass slaughter of chickens in the area H9N2  Several cases of human infection occurred in Hong Kong and Southern China in 1999  The disease was mild and all patients made a complete recovery
  10. 10. Symptoms  Usually much more severe than, the "common cold."  “Incubation period." 1-2 days  Fever (up to 104° F)  Chills  Muscle aches and pains  Sweating  Dry Cough  Nasal congestion  Sore throat  Headache  Malaise & Fatigue  Some or all of these symptoms may be present  Illness can last for up to 1-2 weeks, although fever generally lasts only 3-8 days.
  11. 11. Complications  Bacterial pneumonia  Influenza can damage the lining of the respiratory tract and bacteria establish an infection  Streptococcus pneumoniae and Staphylococcus aureus are the common causes.  Pneumonia caused by the virus itself is less common
  12. 12. Laboratory Diagnosis Specimens  Nasopharyngeal aspirates & throat washings Detection of Antigen  By IFT and ELISA: a rapid diagnosis Virus Isolation Serology  CFT most widely used.  EIA detect type-specific antibodies
  13. 13. Management  Amantidine  Rimantidine  Ribavirin  Neuraminidase inhibitors
  14. 14. Prevention  Vaccination with an inactivated trivalent vaccine, consisting of one A H3N2 strain, one A H1N1 strain, and one B strain  May be 30-90% protective  Given to debilitated, elderly and immunocompromized individuals  Amantidine prophylaxis  WHO Global Surveillance Nasal Spray
  15. 15. Common Cold Viruses  Common colds: one-third to one-half of all acute respiratory infections in humans  Rhinoviruses (30-50%)  Coronaviruses (10-30%)  Others:  Adenoviruses  Enteroviruses  RSV  Influenza, and parainfluenza viruses
  16. 16. Rhinovirus  ssRNA virus  Picornavirus family  Acid-labile  At least 100 serotypes are known Reconstructed Image of rhinovirus particle (Institute for Molecular Virology)
  17. 17. Coronavirus  ssRNA Virus  Enveloped, pleomorphic morphology
  18. 18. Severe Acute Respiratory Syndrome (SARS)  In late 2002: first observed in Southern China (Guangdong Province).  Now been reported in Asia, North America, and Europe  The initial outbreak of SARS peaked in April 2003 and by June had tailed off. By that time, there had been about 8,000 cases worldwide and 775 deaths.
  19. 19. SARS Is characterized by:  Fever above 38o C (100.4o F) headache, general malaise and aches.  Initially mild respiratory symptoms  Dry non-productive cough & dyspnea  Respiratory distress leads to death in 3-30% of cases.
  20. 20. Day 5 Day 10 Day 13 Day 15
  21. 21.  The virus was grown on monkey Vero E6 cells in tissue culture and a new coronavirus (SARS-coV) was identified  Reduction in lymphocyte numbers  Raised aminotransferase activity which indicates damage to the liver. SARS
  22. 22. CDC recommendations:  Chest radiograph  Blood cultures  Sputum Gram's stain and culture  Testing for viral respiratory pathogens, notably influenza A and B and RSV.  Legionella and pneumococcal urinary antigen testing SARS: Lab Diagnosis
  23. 23. Treatment  Suspected SARS patient should be isolated and quarantined.  Management of symptoms  No vaccine against the SARS virus.  A major problem with live virus vaccine is antigenic shift and unpredictable outcomes
  24. 24. Parainfluenza Virus  ssRNA virus  Enveloped  5 serotypes: 1, 2, 3, 4a and 4b  Closely related to Mumps virus (Linda Stannard, University of Cape Town, S.A.)
  25. 25. Clinical Manifestations Croup (laryngotraheobroncitis)  The most common manifestation  Bronchiolitis  Pneumonia  Flu-like tracheobronchitis  Coryza-like illnesses
  26. 26. Laboratory Diagnosis  Specimens  Detection of Antigen  Virus Isolation  Serology  Symptomatic Treatment  No vaccine is available. Management
  27. 27. Respiratory Syncytial Virus (RSV)  ssRNA eveloped virus  Paramyxovirus family  Causes a sizable epidemic each year
  28. 28. Clinical Manifestations  Most common cause of severe lower respiratory tract disease in infants  Bronchiolitis (50-90%)  Bronchopneumonia (5-40% )  Croup (10% of all cases)  Coryza-like illness or bronchitis: in older children and adults
  29. 29. Laboratory Diagnosis Specimens  Nasopharyngeal aspirates & throat washings Detection of Antigen Virus Isolation Serology
  30. 30. Treatment and Prevention  Aerosolised ribavirin  There is no vaccine available  RSV immunoglobulin for high risk group infants
  31. 31. Adenovirus  ds DNA virus  non-enveloped  At least 47 serotypes (Linda Stannard, University of Cape Town, S.A.)
  32. 32. Clinical Syndromes Pharyngitis Pharyngoconjunctival fever Acute respiratory disease of recruits Pneumonia Follicular conjunctivitis Epidemic keratoconjunctivitis Pertussis-like syndrome Acute haemorrhaghic cystitis Acute infantile gastroenteritis Intussusception Severe disease in AIDS Meningitis
  33. 33. Laboratory Diagnosis Specimens  Nasopharyngeal aspirates, throat washings & feces Detection of Antigen Virus Isolation Serology
  34. 34. Treatment and Prevention  A vaccine is available against Adult Respiratory Distress Syndrome.  Consists of live adenovirus 4, 7, and 21 in enterically coated capsules.  Given to new recruits into various arm forces around the world.

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