MicroBiology-Draft/Sample

The Baltimore classification system is an alternative to ICTV nomenclature. The Baltimore system classifies viruses
according to their genomes (DNA or RNA, single versus double stranded, and mode of replication). This system thus
creates seven groups of viruses that have common genetics and biology.

Explore the latest virustaxonomy (http://www.openstaxcollege.org/l/

22virustaxon)at the ICTV website.

Aside from formal systems of nomenclature, viruses are often informally grouped into categories based on chemistry,
morphology, or other characteristics they share in common. Categories may include naked or enveloped structure,
single-stranded (ss) or double-stranded (ds) DNA or ss or ds RNA genomes, segmented or nonsegmented genomes,
and positive-strand (+) or negative-strand (−) RNA. For example, herpes viruses can be classified as a dsDNA
enveloped virus; human immunodeficiency virus (HIV) is a +ssRNA enveloped virus, and tobacco mosaic virus is
a +ssRNA virus. Other characteristics such as host specificity, tissue specificity, capsid shape, and special genes or
enzymes may also be used to describe groups of similar viruses.Table 6.2lists some of the most common viruses
that are human pathogens by genome type.

Common Pathogenic Viruses

Genome Family Example Virus Clinical Features

Poxviridae Orthopoxvirus Skin papules, pustules, lesions

dsDNA, Poxviridae Parapoxvirus Skin lesions

enveloped

Herpesviridae Simplexvirus Cold sores, genital herpes, sexuallytransmitted disease

Adenoviridae Atadenovirus Respiratory infection (common cold)

dsDNA, Papillomaviridae Papillomavirus Genital warts, cervical, vulvar, or vaginalcancer

naked

Reoviridae Reovirus Gastroenteritis severe diarrhea(stomach flu)

Parvoviridae Adeno-associateddependoparvovirus A Respiratory tract infection

ssDNA,

naked

Parvoviridae Adeno-associateddependoparvovirus B Respiratory tract infection

dsRNA,

naked Reoviridae Rotavirus Gastroenteritis

Picornaviridae Enterovirus C Poliomyelitis

+ssRNA,naked Picornaviridae Rhinovirus Upper respiratory tract infection(common cold)

Picornaviridae Hepatovirus Hepatitis

Table 6.2

Link to Learning

Chapter 6 | Acellular Pathogens 237