Lesson 38: Classification of Viruses

International Committee on Taxonomy of Viruses (ICTV)

was established in 1973 to develop and expand the universal scheme in which characteristics of virions are used to assign them to five hierarchical levels (order, family, subfamily, genus and species).

Order: virale

Family: viridae

Subfamily: virinae

Genus: virus

Species: virus

note!

i. Mononegavirale

ii. Nidovirale

Virus Orders:

i. Mononegavirale

Is made up the families Paramyxoviridae, Rhabdoviridae, Bornaviridae and Filoviridae. Members of the order Mononegavirale have common attributes including a single stranded, non-segmented, negative sense RNA genome. Their replication strategies are also similar.

ii. Nidovirale

Comprising of the families Coronaviridae and Arteriviridae.

Poxviruses

Herpes viruses (creeping lesions)

• Some viruses are named according to the type of disease they cause:

Examples:

Acronyms of disease:

Papovavirus (Papilloma - Polyoma - Vacuolating)

Acronym of observable characteristics:

Picornavirus (Pico/Small - RNA - Virus)

• Other are named based on acronyms of disease

Examples:

Coronaviruses (Halo/Corona/Crown of spikes)

Togavirus (Toga/Cloak)

Rhabdovirus (Rhabdo/Rod-shaped)

Calicivirus (Calix/Cup-shaped depression)

• Viruses are also named based on morphology as revealed by electron microscopy

Examples:

Coxsackie

Marburg

Gumboro

Mokola

• Some viruses are named after geographical regions where they were first isolated

Examples:

Example:

Epstein-Barr virus

• Occasionally, viruses are named after individual discoverer

Pathogenicity

In this classification, viruses affecting same tissues producing similar syndrome and pathological manifestations are grouped together.

Influenza

Rhinoviruses

Parainfluenza

Adenovirus

• Viruses affecting the respiratory tract

Examples:

Foot-and-Mouth-Disease

Vesicular Stomatitis

• Vesicular viruses:

Examples:

Rabies

Equine encephalitis

Entroviruses (polio)

Mumps

• Central nervous system viruses:

Examples:

Myxomaviruses

• Mucous membrane viruses:

Example:

Rotaviruses

• Enteric viruses

Example:

viruses

classified into arboviruses and non-arboviruses or roboviruses and nonroboviruses.

• Arboviruses

These are viruses that are transmitted biologically between blood sucking arthropods (such as ticks, culicoides, mosquitoes) and vertebrate hosts. They cause disease in the vertebrate host but not in the arthropods.

African swine fever virus (soft ticks)

Yellow fever virus (mosquitoes)

Equine encephalitis virus (mosquitoes)

African horse sickness virus (culicoides)

• Arboviruses: Examples

• Roboviruses

These are viruses with rodent reservoirs. Infected rodents are asymptomatic. They shed the virus in their urine and contaminate the human surroundings, food, drinks and formites.

Lassa fever virus with rat as reservoir

Roboviruses examples