Table 1.

Virus family descriptors used in virus taxonomy

I Virion properties

A Morphology properties of virions

1 Size

2 Shape

3 Presence or absence of an envelope and peplomers

4 Capsomeric symmetry and structure

B Physical properties of virions

1 Molecular mass

2 Buoyant density

3 Sedimentation coefficient

4 pH stability

5 Thermal stability

6 Cation (Mg2+, Mn2+) stability

7 Solvent stability

8 Detergent stability

9 Radiation stability

C Properties of genome

1 Type of nucleic acid DNA or RNA

2 Strandedness: single-stranded or double-stranded

3 Linear or circular

4 Sense: positive, negative or ambisense

5 Number of segments

6 Size of genome or genome segments

7 Presence or absence and type of 5′ terminal cap

8 Presence or absence of 5′ terminal covalently linked polypeptide

9 Presence or absence of 3′ terminal poly (A) tract (or other specific tract)

10 Nucleotide sequence comparisons

D Properties of proteins

1 Number

2 Size

3 Functional activities (especially virion transcriptase, virion reverse transcriptase, virion hemagglutinin, virion neuraminidase, virion fusion protein)

4 Amino acid sequence comparisons

E Lipids

1 Presence or absence

2 Nature

F Carbohydrates

1 Presence or absence

2 Nature

II Genome organization and replication

1 Genome organization

2 Strategy of replication of nucleic acid

3 Characteristics of transcription

4 Characteristics of translation and post-translational processing

5 Site of accumulation of virion proteins, site of assembly, site of maturation and release

6 Cytopathology, inclusion body formation

III Antigenic properties

1 Serological relationships

2 Mapping epitopes

IV Biological properties

1 Host range, natural and experimental

2 Pathogenicity, association with disease

3 Tissue tropisms, pathology, histopathology

4 Mode of transmission in nature

5 Vector relationships

6 Geographic distribution

Adapted from ICTV guidelines for family descriptions.