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SGSC BIOL 2215K - Chapter 25 The RNA Viruses That Infect Humans

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Foundations in Microbiology Sixth EditionRNA VirusesSlide 3Enveloped Segmented Single-Stranded RNA VirusesThe Biology of Orthomyxoviruses: InfluenzaSlide 6Slide 7Slide 8Slide 9Influenza ADiagnosis, Treatment, PreventionBunyaviruses and ArenavirusesEnveloped Nonsegmented ssRNA VirusesParamyxovirusesSlide 15ParainfluenzaMumpsMeaslesSlide 19Respiratory Syncytial Virus (RSV)RabiesSlide 22Slide 23Slide 24Slide 25CoronavirusesSevere Acute Respiratory Syndrome-Associated Coronavirus (SARS)RubellaSlide 29Slide 30Hepatitis C Virus (HCV)Arboviruses: Viruses Spread by Arthropod VectorsThe Influence of the VectorSlide 34General Characteristics of Arbovirus InfectionsSlide 36Hemorrhagic FeversHIV Infections and AIDSCausative AgentSlide 40Epidemiology of HIV InfectionsSlide 42Slide 43Slide 44Pathogenesis and Virulence Factors of HIVSlide 46Slide 47Signs and Symptoms of HIV Infections and AIDSSlide 49Slide 50Diagnosis of HIV InfectionSlide 52Slide 53Preventing and Treating HIVSlide 55Adult T-Cell Leukemia and Hairy-Cell LeukemiaNonenveloped Nonsegmented ssRNA Viruses: Picornaviruses and CalicivirusesSlide 58Poliovirus and PoliomyelitisSlide 60Slide 61Slide 62Slide 63Treatment and PreventionNonpolio EnterovirusesHepatitis A Virus and Infectious HepatitisSlide 67Human Rhinovirus (HRV)Slide 69Slide 70CalicivirusesNonenveloped Segmented dsRNA Viruses: ReovirusesPrions and Spongiform EncephalopathiesSlide 74Slide 75Slide 76Foundations in MicrobiologySixth EditionChapter 25The RNA Viruses That Infect HumansLecture PowerPoint to accompanyTalaroCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.2RNA Viruses Assigned to one of 12 families based on envelope, capsid, and nature of RNA genome3Insert Table 25.1RNA viruses4Enveloped Segmented Single-Stranded RNA Viruses5The Biology of Orthomyxoviruses: Influenza•ssRNA consists of 10 genes encoded on 8 separate RNA segments.•3 distinct influenza virus types: A, B, C; Type A causes most infections•Virus attaches to, and multiplies in, the cells of the respiratory tract; finished viruses are assembled and budded off.6Insert figure 25.1Influenza cycle7•Key to influenza are glycoprotein spikes – –hemagglutinin (H) – 15 different subtypes; most important virulence factor; binds to host cells–neuraminidase (N) – 9 subtypes – hydrolyzes mucus and assists viral budding and release•Both glycoproteins frequently undergo genetic changes decreasing the effectiveness of the host immune response.•Constant mutation is called, antigenic drift - gradually change their amino acid composition•Antigenic shift – one of the genes or RNA strands is substituted with a gene or strand from another influenza virus from a different animal host8Insert figure 25.3Antigenic shift9Influenza B•Not known to undergo antigenic shiftInfluenza C•Known to cause only minor respiratory disease; probably not involved in epidemics10Influenza A•Acute, highly contagious respiratory illness•Seasonal, pandemics; among top 10 causes of death in U.S.- most commonly among elderly and small children•Respiratory transmission•Binds to ciliated cells of respiratory mucosa•Causes rapid shedding of cells, stripping the respiratory epithelium; severe inflammation•Fever, headache, myalgia, pharyngeal pain, shortness of breath, coughing•Weakened host defenses predispose patients to secondary bacterial infections, especially pneumonia.11Diagnosis, Treatment, Prevention•Rapid immunofluorescence tests to detect antigens in a pharyngeal specimen; serological testing to screen for antibody titer•Treatment: control symptoms; amantadine, rimantadine, zanamivir (Relenza) and oseltamivir (Tamiflu)•Flu virus has developed high rate of resistance to amantadine and rimantadine.•Annual trivalent vaccine recommended12Bunyaviruses and Arenaviruses•Transmitted zoonotically; cause periodic epidemics; extremely dangerous; biosafety level 4 virusesBunyaviruses – transmitted by insects and ticks–California encephalitis, Rift Valley fever, Korean hemorrhagic fever–American bunyavirus is a hantavirus, Sin Nombre – emerging disease; high fever, lung, edema, and pulmonary failure; 33% mortality rate•carried by deer and harvest mice; transmitted via airborne dried animal wasteArenaviruses•Lassa fever, Argentine hemorrhagic fever, Bolivian hemorrhagic fever, and Lymphocytic chroiomeningitis•Closely associated with rodent host•Transmission through aerosols and contact13Enveloped Nonsegmented ssRNA Viruses14ParamyxovirusesParamyxoviruses (parainfluenza, mumps virus)Morbillivirus (measles virus)Pnuemonovirus (respiratory syncytia virus)•Respiratory transmission•Envelope has HN and specialized F spikes that initiate cell-to-cell fusion.•Fusion with neighboring cells – syncytium or multinucleate giant cells form15Insert figure 25.5Effects of paramyxoviruses16Parainfluenza•Widespread as influenza but more benign•Respiratory transmission•Seen mostly in children•Minor cold, bronchitis, bronchopneumonia, croup•No specific treatment available; supportive therapy17Mumps•Epidemic parotitis; self-limited, associated with painful swelling of parotid salivary glands•Humans are the only reservoir.•40% of infections are subclinical; long-term immunity.•300 cases in U.S./year•Incubation 2-3 weeks fever, muscle pain and malaise, classic swelling of one or both cheeks•Usually uncomplicated invasion of other organs; in 20-30% of infected adult males, epididymis and testes become infected; sterility is rare•Symptomatic treatment•Live attenuated vaccine MMR18Measles•Caused by Morbillivirus•Also known as red measles and rubeola•Different from German measles•Very contagious; transmitted by respiratory aerosols•Humans are the only reservoir.•Less than 100 cases/yr in U.S.; frequent cause of death worldwide•Virus invades respiratory tract.•Sore throat, dry cough, headache, conjunctivitis, lymphadenitis, fever, Koplik spots – oral lesions•Exanthem19Measles•Most serious complication is subacute sclerosing panencephalitis (SSPE), a progressive neurological degeneration of the cerebral cortex, white matter and brain stem.•1 case in a million infections•Involves a defective virus spreading through the brain by cell fusion and destroys cells•Leads to coma and death in months or years•Attenuated viral vaccine MMR20Respiratory Syncytial Virus (RSV)•Also called Pneumovirus•Infects upper


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