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Classification of Medically Important Viruses @ Two components of virus are used

Classification of Medically Important Viruses @ Two components of virus are used in classification : 1. Molecular weight & structure of nucleic acid 2. Size, symmetry ,& envelope of capsid. DNA VIRUSES 3 nonenveloped, icosahedral virus families:*parvoviruses,

stephanie-gutierrez
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Classification of Medically Important Viruses @ Two components of virus are used

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  1. Classification of Medically • Important Viruses • @ Two components of virus are used • in classification : • 1. Molecular weight & structure of • nucleic acid • 2. Size, symmetry ,& envelope of • capsid

  2. DNA VIRUSES • 3 nonenveloped, icosahedral virus • families:*parvoviruses, • *papovaviruses, *adenoviruses • 2. 3 enveloped virus families : a) hepadnavirus family, eg : • hepatitis B virus – icosahedral b) herpesviruses - icosahedral . c) pox viruses - complex symmetry

  3. Papovaviruses • @ Nonenveloped (naked) icosahedral viruses , with double-stranded circular DNA. • @ Known: papilloma, polyoma, simian viruses • @ 3 human papovaviruses known : • JC virus, isolated from progressive multifocal leukoencephalopathy cases . • BK virus, isolated from urine of kidney transplant patients . • Human papillomavirus

  4. Adenoviruses @ Naked icosahedral, Ds. linear DNA viruses @ Cause pharyngitis, URT & LRT diseases . @ There are at least 40 antigenic types .

  5. Parvoviruses • @ Very small, nonenveloped, icosahedral, Ss. , linear DNA. • @ 2 types of parvoviruses: Defective & nondefective : • Defective require a helper virus for replication. • Nondefective ,e.g. B 19 virus

  6. Hepadnaviruses @ These are double-stranded viruses with an icosahedral capsid covered by an envelope. @ Hepatitis B virus is the human pathogen in this family.

  7. Herpesviruses @ Enveloped, icosahedral, Ds., linear DNA viruses @ Cause latent infections. @ The 5 important pathogens: *herpes simplex types I & 2, *varicella-zoster, *CMV *Epstein-Barr cause of IM.

  8. Poxviruses @ Largest virus with a bricklike shape, an envelope, & a complex capsid symmetry. @ Cause skin lesions, or "pocks" @ Smallpox & vaccinia are the two important members. @ Vaccinia virus is used in smallpox vaccine.

  9. RNA VIRUSES @ 14 families of RNA viruses . @ 3 naked icosahedral viruses : 1. Picornavirus 2. Calicivirus 3. Reovirus @ 3 enveloped icosahedral viruses: 1. Flavivirus 2. Togavirus 3. Retrovirus

  10. @ 8 are enveloped helical viruses: * 5 have Ss. linear RNA, e.g: (1) orthomyxovirus (2) paramyxovirus (3) rhabdovirus (4) filovirus (5) coronavirus * 3 have Ss. circular RNA, e.g: (1) arenavirus (2) bunyavirus (3) deltavirus .

  11. Picornaviruses @ The smallest RNA viruses. @ Have Ss, linear, nonsegmented RNA within a naked icosahedral capsid. @ "picorna" is derived from pico- small @ Divided into 2 groups of pathogens: (I) enteroviruses : poliovirus, echovirus coxsackievirus, hepatitis A (2) rhinoviruses.

  12. Caliciviruses @ Naked , icosahedral viruses. @ Have Ss, linear, nonsegmented, RNA. @ 2 human pathogens: * Norwalk virus * hepatitis E virus.

  13. Reoviruses @ Naked viruses with 2 icosahedral capsid coats. @ Have 10 segments of Ds. linear RNA. @ Main pathogen is rotavirus, causing diarrhea in infants.

  14. Flaviviruses • @ Enveloped, icosahedral, Ss, linear, nonsegmented, RNA viruses • @ Include : • hepatitis C virus, • yellow fever virus, • dengue virus, • St. Louis encephalitis viruses. • Japanese encephalitis viruses.

  15. Togaviruses @ Enveloped, icosahedral, Ss, linear, nonsegmented RNA viruses @ 2 groups of human pathogens: * Alphaviruses: include : eastern & western encephalitis viruses * Rubiviruses: contain only rubella virus

  16. Retroviruses • @ Enveloped, icosahedral, with 2 strands of Ss , linear RNA viruses • @ "retro" pertains to the reverse transcription of RNA into DNA. • @ 2 medically important groups: • oncovirus group, contains the sarcoma & leukemia viruses, e.g. • (human T cell leukemia virus-HTLV) • 2.lentivirus group includes human immunodeficiency virus (HIV) .

  17. Orthomyxoviruses @ Enveloped, with a helical capsid & 8 segments oflinear, Ss RNA. @ "myxo" means affinity formucins. @ Influenza virus is the main human pathogen.

  18. Paramyxoviruses @ Enveloped, helical, Ss , linear, non segmented RNA viruses @ Human pathogens are : *measles, *mumps, *parainfluenza, *respiratory syncytial (RSV).

  19. Rhabdoviruses @ Bullet-shaped enveloped viruses with a helical, Ss , linear, nonsegmented RNA viruses @"rhabdo" refers to bullet shape. @ Rabies virus is the only important human pathogen.

  20. Filoviruses @ Enveloped, helical, Ss , linear, nonsegmented RNA viruses. @ Pleomorphic, long filaments . @ "filo" means "thread" . @ 2 human pathogens are : *Ebola virus *Marburg virus.

  21. Coronaviruses @ Enveloped, helical, Ss , linear, nonsegmented RNA viruses . @ "corona" refers to crown of spikes protruding from envelope. @ Cause respiratory tract infections (e.g. common cold) .

  22. Arenaviruses @ Enveloped, helical, Ss, circular, 2 segments RNA viruses @ "arena" is "sand“, refers to ribosome granules on virus surface @ 2 human pathogens are known : *lymphocytic choriomeningitis virus *Lassa fever virus.

  23. Bunyaviruses @ Enveloped, helical, Ss, circular 3 segments RNA viruses . @ "bunya" refers to the place in Africa where it was isolated. @ Cause encephalitis & fevers e.g Korean hemorrhagic fever.

  24. Deltavirus @ Hepatitis delta virus (HDV) is the only member of this genus. @ Enveloped, helical, circular, Ss, RNA virus @ It is a defective virus “cannot replicate unless hepatitis B virus (HBV) is present within the same cell”

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