questions 2

RNA Viruses

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Topic updated on 10/06/15 12:15am

Microbiology Overview
 

 
RNA Virus Table
 
RNA Positive-Stranded
  Disease Treatment or Vaccine
Poliovirus Paralytic poliomyelitis (paralysis)
Aseptic meningitis
Post-polio syndrome
Sabin vaccine (live)
SalK vaccine (Killed)
Rhinovirus Common cold (most common cause) No specific treatment
Coxsackievirus Aseptic meningitis
Carditis
Hand, foot, and mouth disease
Herpangia
Pleurodynia
Bornholm disease (Devil's grip)
No specific treatment
Echovirus Aseptic meningitis --
Hepatitis A virus Mild acute hepatitis Killed vaccine
Serum globulin
Calicivirus
Norwalk virus Acute gastroenteritis (schoolchildren) No specific treatment
Togavirus
Rubella virus Rubella (German measles)
Congenital rubella
Live attenuated vaccine (MMR)
Eastern equine encephalitis   Killed vaccine
Western equine encephalitis   Killed vaccine
Flavivirus
Yellow fever virus Yellow fever Live attenuated vaccine
Dengue Dengue ("break bone fever") Supportive only
Hepatitis C virus Chronic hepatitis IFN, ribavirin
West Nile virus Aseptic meningitis
Encephalitis
Paralysis
Supportive only
St. Louis encephalitis Encephalitis Supportive only
Coronavirus
Coronavirus Common cold
SARS
Self-limiting
Retrovirus 
HIV AIDS HAART
Human T cell leukemia virus T-cell leukemia --
Hepevirus
Hepatitis E virus Mild acute hepatitis
(fatal when prEgnant)
Self-limiting
RNA Negative-Stranded
Bunyavirus
Hantavirus Hantavirus pulmonary syndrome (50% mortality) Supportive only
CA Encephalitis virus Encephalitis --
Orthomyxovirus
Influenza virus Flu Zanamivir/oseltamivir
Paramyxovirus
Rubeola Measles Live attenuated vaccine (MMR)
Mumps virus Mumps Live attenuated vaccine (MMR)
RSV Pneumonia (infants) Palivizumab
Parainfluenza Croup
Bronchiolitis
Pneumonia
Supportive only
Rhabdovirus
Rabies virus Rabies hRIG
Arenavirus
Lassa fever virus Hemorrhagic fever (50% mortality) Ribavirin
Lymphocytic choriomeningitis virus (LCMV) Meningitis --
Filovirus
Ebola and marburg viruses Hemorrhagic fever (up to 90% mortality) Supportive only
RNA Double-Stranded
Reovirus
Reovirus Common cold
Gastroenteritis
Self-limiting
Rotavirus Gastroenteritis (infants) Self-limiting
Colorado tick fever virus Flu-like Supportive only
 
Virus Overview
  • Viruses are obligate intracellular infectious agents with the following basic components
    • DNA or RNA
      • never both
    • capsid
      • a protein coat that surrounds the genetic material
      • icosahedral or helical symmetry
      • made of capsomers
        • polypeptide chains organized into a globular subunit
        • in helical symmetry, capsomers are bound to RNA and coiled
          • forms a helical nucleoprotein capsid
    • sometimes an envelope
  • Viruses are classified by
    • nucleic acid
      • DNA or RNA
      • double stranded or single stranded
      • (+) or (-) stranded RNA
      • single or segmented pieces of nucleic acid
      • complexity of genome
    • capsid
      • icosahedral or helical
    • envelope
      • naked
        • DNA or RNA + capsomers and other structural proteins = nucleocapsid
      • enveloped
        • nucleocapsid + host membrane with viral-specified glycoproteins = enveloped virus
    • size
      • diameter or number of capsomers
    • ploidy
      • all viruses are haploid (1 copy of DNA or RNA)
      • except retroviruses
        • retroviruses have 2 identical copies of their ssRNA, approximating diploidy
    • infectivity of purified nucleic acid
      • purified nucleic acid that is intrinsically infectious
        • dsDNA from most viruses
          • except poxviridae
          • except HBV
        • (+) strand ssRNA from most viruses
          • (+) linear, nonsegmented ssRNA can be translated immediately into a large protein by host machinery
          • virus must carry protease to cleave the 1 large protein product that will be generated by the host machinery
      • purified nucleic acid that is NOT intrinsically infectious
        • (-) ssRNA
          • viruses must carry an RNA-dependent RNA polymerase to generate mRNA the host machinery can read
        • dsRNA
        • they require enzymes contained in the complete virion for infectivity
RNA Viruses
  • Most RNA viruses
    • are single-stranded (ssRNA, like human mRNA)
    • have helical symmetry
    • replicate in the cytoplasm
    • are enveloped
  • Exceptions
    • double-stranded (dsRNA) (1)
      • reo
    • icosahedral (5)
      • reo
      • picorna
      • toga
      • flavi
      • calici
    • replicate in nucleus (2)
      • retro
      • orthomyxo
    • non-enveloped (3)
      • picorna
      • calici
      • reo


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