Respiratory Viruses - Microbiology - Lecture Slides, Slides of Microbiology

Download Respiratory Viruses - Microbiology - Lecture Slides and more Slides Microbiology in PDF only on Docsity! Respiratory Viruses An Overview Docsity.com Viruses Associated with Respiratory Infections Syndrome Commonly Associated Viruses Less Commonly Associated Viruses Corza Rhinoviruses, Coronaviruses Influenza and parainfluenza viruses, enteroviruses, adenoviruses Influenza Influenza viruses Parainfluenza viruses, adenoviruses Croup Parainfluenza viruses Influenza virus, RSV, adenoviruses Bronchiolitis RSV Influenza and parainfluenza viruses, adenoviruses Bronchopneumonia Influenza virus, RSV, Adenoviruses Parainfluenza viruses, measles, VZV, CMV Docsity.com Epidemiology • Pandemics - influenza A pandemics arise when a virus with a new haemagglutinin subtype emerges as a result of antigenic shift. As a result, the population has no immunity against the new strain. Antigenic shifts had occurred 3 times in the 20th century. • Epidemics - epidemics of influenza A and B arise through more minor antigenic drifts as a result of mutation. Docsity.com 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-emergenceNo pandemic 2009 H1N1 “Swine Flu Mild 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. Docsity.com Avian Influenza H5N1 • An outbreak of Avian Influenza H5N1 occurred in Hong Kong in 1997 where 18 persons were infected of which 6 died. • The source of the virus was probably from infected chickens and the outbreak was eventually controlled by a mass slaughter of chickens in the territory. • All strains of the infecting virus were totally avian in origin and there was no evidence of reassortment. • However, the strains involved were highly virulent for their natural avian hosts. H9N2 • Several cases of human infection with avian H9N2 virus occurred in Hong Kong and Southern China in 1999. • The disease was mild and all patients made a complete recovery • Again, there was no evidence of reassortment Docsity.com Management • Neuraminidase inhibitors - are now the drugs. They are highly effective and have fewer side effects than amantidine. Oseltamivir (Tamiflu) is the most commonly used agent as it can be given orally unlike Zanamivir (Relenza). The resistance to different types varies enormously year to year. H3N2 strains were mainly sensitive whereas seasonal H1N1 were almost totally resistant. More than 98% of the 2009 pandemic influenza H1N1 tested were sensitive. • Amantidine is effective against influenza A if given early in the illness. However, resistance to amantidine emerges rapidly. Rimantidine is similar to amantidine but but fewer neurological side effects. • Ribavirin is thought to be effective against both influenza A and B. Docsity.com Prevention • Inactivated split/subunit vaccines are available against influenza A and B. • The vaccine is normally trivalent, consisting of one A H3N2 strain, one A H1N1 strain, and one B strain. • The strains used are reviewed by the WHO each year. • The vaccine should be given to debilitated and elderly individuals who are at risk of severe influenza infection. • Amantidine can be used as an prophylaxis for those who are allergic to the vaccine or during the period before the vaccine takes effect. Docsity.com Parainfluenza Virus • ssRNA virus • enveloped, pleomorphic morphology • 5 serotypes: 1, 2, 3, 4a and 4b • No common group antigen • Closely related to Mumps virus Docsity.com Management • No specific antiviral chemotherapy available. • Severe cases of croup should be admitted to hospital and placed in oxygen tents. • No vaccine is available. Docsity.com Respiratory Syncytial Virus (RSV) • ssRNA eveloped 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. Docsity.com Clinical Manifestations • Most common cause of severe lower respiratory tract disease in infants, responsible for 50-90% of Bronchiolitis and 5-40% of Bronchopneumonia • Other manifestations include croup (10% of all cases). • In older children and adults, the symptoms are much milder: it may cause a corza-like illness or bronchitis. Docsity.com Treatment and Prevention • Aerosolised ribavirin can be used for infants with severe infection, and for those at risk of severe disease. • There is no vaccine available. • RSV immunoglobulin can be used to protect infants at risk of severe RSV disease. Docsity.com Adenovirus • ds DNA virus • non-enveloped • At least 47 serotypes are known • classified into 6 subgenera: A to F Docsity.com Clinical Syndromes 1. Pharyngitis 1, 2, 3, 5, 7 2. Pharyngoconjunctival fever 3, 7 3. Acute respiratory disease of recruits 4, 7, 14, 21 4. Pneumonia 1, 2, 3, 7 5. Follicular conjunctivitis 3, 4, 11 6. Epidemic keratoconjunctivitis 8, 19, 37 7. Pertussis-like syndrome 5 8. Acute haemorrhaghic cystitis 11, 21 9. Acute infantile gastroenteritis 40, 41 10. Intussusception 1, 2, 5 11. Severe disease in AIDS and other immunocompromized patients 5, 34, 35 12. Meningitis 3, 7 Docsity.com Common Cold Viruses • Common colds account for one-third to one-half of all acute respiratory infections in humans. • Rhinoviruses are responsible for 30-50% of common colds, coronaviruses 10-30%. • The rest are due to adenoviruses, enteroviruses, RSV, influenza, and parainfluenza viruses, which may cause symptoms indistinguishable to those of rhinoviruses and coronaviruses. Docsity.com Rhinovirus • ssRNA virus • Belong to the picornavirus family • ssRNA virus • acid-labile • at least 100 serotypes are known Docsity.com Coronavirus • ssRNA Virus • Enveloped, pleomorphic morphology • 2 serogroups: OC43 and 229E Docsity.com