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Orthomyxoviruses & Paramyxoviruses Overview

Learn about Orthomyxoviruses like Influenza A/B/C, Antigenic Shift, Pathology, Vaccines, Chemoprophylaxis, and Paramyxoviruses Family including Measles, Mumps, Parainfluenza virus, and RS-virus structure and transmission.

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Orthomyxoviruses & Paramyxoviruses Overview

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  1. ORTHOMYXOVIRUSES PARAMYXOVIRUSES

  2. Orthomyxovirus

  3. Orthomyxovirus Family The name myxovirus was originally applied to influenza viruses. It meant virus with an affinity for mucins.

  4. A model of the influenza virion

  5. Types:A, B, C Influenza A: In Birds • 16 H variants • 9 N variants In Humans • 3 H variants (H1, H2, and H3) • 2 N variants (N1 and N2) Subtypes:H1N1, H2N2,H2N3

  6. Swine New Reassorted virus Human virus Avian virus Avian Reservoir Other mammals? Influenza Viruses:Antigenic Shift

  7. Gradual accumulation of mutations that allow the hemagglutinin to escape neutralizing antibodies (Point mutation in HA gene) • Epidemic strains thought to have changes in three or more antigenic sites Influenza Viruses:Antigenic Drift

  8. Pathogenesis and Pathology The virus enters the respiratory tract in airborne droplets. Viremia is rare. Virus is present in the nasopharynx from 1-2 days before to 1-2 days after onset of symptoms. Inflammation of the upper respiratory tract causes necrosis of the ciliated and goblet cells of the tracheal and bronchial mucosa but does not affect the basal layer of epithelium. Interstitial pneumonia may occur with necrosis of bronchiolar epithelium and may be fatal. The pneumonia is often associated with secondary bacterial invaders: staphylococci, pneumococci, streptococci, and Haemophilus influenzae.

  9. Clinical Findings The incubation period is 1 or 2 days. Chills, malaise, fever, muscular aches, prostration, and respiratory symptoms may occur. The fever persists for about 3 days; complications are not common, but pneumonia, myocarditis, pericarditis, and central nervous system complications occur rarely. The latter include encephalomyelitis, polyneuritis, Guillain-Barre syndrome, and Reye's syndrome (see below).

  10. Whole virus vaccine: inactivated virus vaccine grown in embryonated eggs; 70-90% effective in healthy persons <65 years of age, 30-70% in persons ≥65 years • Split virus vaccine: previously associated with fewer systemic reactions among the elderly and children <12 years • Subunit vaccine: composed of H and N • Live, attenutated influenza virus vaccines under development Influenza Vaccines

  11. Amantadine and rimantadine: effective against type A, but not type B, influenza viruses; block the M2 ion channel • 70-90% effective in preventing illness • Administered to individuals at high risk of complications who are vaccinated after outbreak of infection, persons with immune defficiency Influenza: Chemoprophylaxis

  12. Amantadine (adults and children ≥ 1 year) and rimantadine (adults) • Zanamivir and oseltamivir: neuraminidase inhibitors active against both type A and B influenza viruses • Reduce duration of illness by ~1 day when administered within 2 days of the onset of illness (uncomplicated influenza) Influenza: Chemotherapy

  13. Laboratory Diagnosis Throat washings or garglings are obtained within 3 days after onset and should be tested at once or stored frozen. Penicillin and streptomycin are added to limit bacterial contamination. For rapid detection of influenza virus in clinical specimens, positive smears from nasal swabs may be demonstrated by specific staining with fluorescein-labeled antibody. Paired sera are used to detect rises in HI, CF, or Nt antibodies.

  14. Paramyxoviruses

  15. FamilyParamyxoviridae Genes: Morbillivirus– measles virus, Respirovirus– parainfluenza virus(serotypes1 and 3) Rubulavirus - mumps virus,parainfluenza virus(serotypes 2, 4а, 4b), Pneumovirus – RS-virus

  16. pleomorphic HN/H/G glycoprotein SPIKES F glycoprotein SPIKES helical nucleocapsid (RNA minus NP protein) lipid bilayer membrane polymerase complex PARAMYXOVIRUSES M protein

  17. STRUCTURE-PARAMYXOVIRUSES

  18. Cell fusion. In the course of infection, paramyxo-viruses cause cell fusion, long recognized as giant cell formation.

  19. MUMPS (Epidemic Parotitis) Mumps is an acute contagious disease characterized by a nonsuppurative enlargement of one or both of the parotid glands, although other organs may also be involved. Properties of the Virus:The mumps virus particle has the typical paramyxovirus morphology. Typical also are the biologic properties of hemagglutination, neuraminidase, and hemolysin.

  20. Epidemiology The disease reaches its highest incidence in children age 5-15 years, but epidemics occur in army camps. Humans are the only known reservoir of virus. The virus is transmitted by direct contact, airborne droplets, or fomites contaminated with saliva and, perhaps, urine. The period of communicability is from about 4 days before to about a week after the onset of symptoms.

  21. Pathogenesis and Pathology The virus travels from the mouth to the parotid gland, where it undergoes primary multiplication. This is followed by a generalized viremia and localization in testes. ovaries, pancreas, thyroid, or brain. The ducts of the parotid glands show desquamation of the epithelium, and polymorphonuclear cells are present in the lumens. There are interstitial edema and lymphocytic infiltration.

  22. Orchitis

  23. PARAINFLUENZA VIRUS The parainfluenza viruses are paramyxoviruses with morphologic and biologic properties typical of the genus. They grow welt in primary monkey or human epithelial cell culture but poorly or not at all in the embryonated egg. They produce a minimal cytopathic effect in cell culture but are recognized by the hemadsorption method. Laboratory diagnosis may be made by the HI, CF, and Nt tests.

  24. PIV STRUCTURE

  25. MEASLES (Rubeola) Measles is an acute, highly infectious disease characterized by a maculopapular rash, fever, and respiratory symptoms. Properties of the Virus: Measles virus is a typical paramyxovirus. It lacks neuraminidase activity.

  26. Measles virus

  27. Pathogenesis and Pathology Infection is contracted by inhalation of droplets expelled in sneezing or coughing. Measles is spread during the catarrhal prodromal period; they are infectious from 1-2 days prior to the onset of symptoms until a few days after the rash has appeared The virus enters the respiratory tract, enters cells, and multiplies there. During the prodrome, the virus is present in the blood, throughout the respiratory tract, and in nasopharyngeal, tracheobronchial, and conjunctival secretions. It persists in the blood and nasopharyngeal secretions for 2 days after the appearance of the rash. Transplacental transmission of the virus can occur.

  28. Pathogenesis and Pathology Koplik's spots are vesicles in the mouth formed by focal exudations of serum and endothelial cells, followed by focal necrosis. In the skin the superficial capillaries of the corium are first involved, and it is here that the rash makes its appearance. Generalized lymphoid tissue hyperplasia occurs. Multinucleate giant cells are found in lymph nodes, tonsils, adenoids, spleen, appendix, and skin. In encephalomyelitis, there are petechial hemorrhages, lymphocytic infiltration, and later, patchy demyelination in the brain and spinal cord.

  29. Koplik's spots

  30. RESPIRATORY SYNCYTIAL (RS) VIRUS This labile paramyxovirus produces a characteristic syncytial effect, the fusion of cells in human cell culture. It is the single most serious cause of bronchiolitis and pneumonitis in infants. Properties of the Virus:RS virus does not hemagglutinate.

  31. RSV- Structure immunofluoresent stain

  32. RSV- syncytium formation

  33. This disease is transmitted by coughing, sneezing, sharing wash cloths towels and other things with someone with RSV. Pathogenesis and Pathology This disease is extremely serious when it comes to children and infants under the age of 3 and elders. This disease can result in death.

  34. Symptoms for this disease are: sneezing, runny nose, sore throat, low fever, common cold symptoms just more severe. Treatment: Supportive Fluids, oxygen, respiratory support, bronchodilators Antiviral Agents Ribavirin (Virazole), a synthetic guanosine analogue, given as an aerosol RSV Bronchiolitis- clinical features

  35. Combination live virus vaccines (measles-mumps-rubella) • Live attenuated measles virus vaccine effectively prevents measles. Prophylaxis

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