Table 2-2

Properties of Virions of Families of RNA Viruses Infecting Humans

Virion

Nucleoscapid

Genome

Family

Diameter (nm)a

Envelope

Symmetry

Capsomers

Transcriptase

Natureb

Size (kb,kbp)

Picornavir.

25-30

-

Icosahedral

60

-

ss +

7.5-8.5

Caliciviridae

35-40

-

Icosahedral

32

-

ss +

8

Astroviridae

28-30

-

Icosahedral

?

-

ss, +

7.5

Togaviridae

60-70

+c

Icosahedral

60

-

ss, +

12

Flaviviridae

40-50

+c

Icosahedral

?

-

ss, +

10

Coronavir.

75-160

+c

Helical

?

-

ss, +

27-33

Paramyxovir

150-300

+

Helical

?

+

ss, -

15-16

Rhabdovir.

180 x 75

+

Helical

?

+

ss -

13-16

Filoviridae

790-970 x 80

+

Helical

?

+

ss, -

12.7

Orthomyxo

80-120

+

Helical

?

+

ss, 7-8, -

13.6

Arenaviridae

110-130

+c

Helical

?

+

ss, 2, -

10-14

Bunyavir.

90-120

+c

Helical

?

+

ss, 3, -

13.5-21

Reoviridae

60-80

-

Icosahedral

32, 92d

+

ds, 10-12e

18-27

Retroviridae

80-100

+c

Icosahedral

?

+f

ss, +

7-10g

Deltavirus

32

-

Icosahedral

?

_

ss, -, circular

1.7

a Some enveloped viruses are very pleomorphic and sometimes filamentous.

b All genomes except that of Deltavirus are linear; ss, single-stranded; ds, double-stranded; 2 to 12, number of

segments in segmented genomes; + or -, sense of single-stranded nucleic acid.

c No matrix protein.

d 32, inner capsid of Orbivirus, Rotavirus, an Orthoreovirus; 92, outer capsid of Orthoreovirus.

e Orthoreovirus and Orbivirus, 10; Rotavirus, 11; and Coltivirus, 12.

f Reverse transcriptase.

g Genome is diploid, two identical molecules being held together by hydrogen bonds at their 5' ends.