Page 259 - Review of Medical Microbiology and Immunology ( PDFDrive )

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31
T
E
C
R
Classification of Medically

Important Viruses

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CHAPTER C ONTENT S

Principles of Classification
Togaviruses
DNA Viruses
Parvoviruses
Retroviruses
Orthomyxoviruses
Polyomaviruses
Papillomaviruses
Paramyxoviruses
Adenoviruses
Hepadnaviruses
Filoviruses
Herpesviruses Rhabdoviruses
Coronaviruses
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Arenaviruses
Poxviruses
RNA Viruses
Bunyaviruses
Picornaviruses
Deltavirus
Hepeviruses
Caliciviruses
Practice Questions: USMLE & Course Examinations
Reoviruses

PRINCIPLES OF CLASSIFICATION
metry and whether it is enveloped). A classification scheme
The classification of viruses is based on chemical and mor-
based on these factors is presented in Tables 31–1 and 31–2
phologic criteria. The two major components of the virus weight and structure) and (2) the capsid (its size and sym-
for DNA and RNA viruses, respectively. This scheme was
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mebooksfree.com mebooksfree.com Capsid Virion Size DNA MW DNA Structure 1 Medically Important Viruses mebooksfree.com
used in classification are (1) the nucleic acid (its molecular
simplified from the complete classification to emphasize
TABLE 31–1 Classification of DNA Viruses
Envelope
6
Virus Family
(×10 )
Present
(nm)
Symmetry
2
B19 virus
SS, linear
Icosahedral
No
22
Parvovirus
JC virus, BK virus
Icosahedral
No
DS, circular, supercoiled
45
Polyomavirus
3
Papillomavirus
Adenovirus
75
Icosahedral
No
Adenovirus
DS, linear
Hepatitis B virus
DS, incomplete circular
42
Yes
Icosahedral
1.5
Hepadnavirus No Icosahedral 55 2 5 23 DS, circular, supercoiled Human papillomavirus
Herpes simplex virus, varicella-
Yes
Herpesvirus
Icosahedral
DS, linear
100–150
100
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zoster virus, cytomegalovirus,
Epstein–Barr virus
Poxvirus
Yes
contagiosum virus
1
SS = single-stranded; DS = double-stranded.
2
The herpesvirus nucleocapsid is 100 nm, but the envelope varies in size. The entire virus can be as large as 200 nm in diameter.
248
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