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

DNA VIRUSES 1. 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

Nonenveloped (naked) icosahedral viruses, with double-stranded circular Known: papilloma, polyoma, simian 3 human papovaviruses known : 1.JC virus, isolated from progressive multifocal leukoencephalopathy cases. 2.BK virus, isolated from urine of kidney transplant patients. 3.Human papillomavirus

Naked icosahedral, Ds. linear DNA Cause pharyngitis, URT & LRT There are at least 40 antigenic types.

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

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

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

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

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

@ 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.

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

Naked, icosahedral Have Ss, linear, nonsegmented, 2 human pathogens: * Norwalk virus * hepatitis E virus.

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

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

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

Enveloped, icosahedral, with 2 strands of Ss, linear RNA "retro" pertains to the reverse transcription of RNA into 2 medically important groups: 1.oncovirus group, contains the sarcoma & leukemia viruses, e.g. (human T cell leukemia virus-HTLV) 2.lentivirus group includes human immunodeficiency virus (HIV).

Enveloped, with a helical capsid & 8 segments of linear, Ss "myxo" means affinity for Influenza virus is the main human pathogen.

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

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

Enveloped, helical, Ss, linear, nonsegmented RNA Pleomorphic, long "filo" means 2 human pathogens are : *Ebola virus *Marburg virus.

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

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

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

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