Orthornavirae

Orthornavirae is a realm of RNA viruses that includes all viruses with a positive-sense, negative-sense, or double-stranded RNA genome. This realm is part of the larger Riboviria realm, which encompasses all RNA viruses that replicate via an RNA-dependent RNA polymerase. The name "Orthornavirae" is derived from the Greek "ortho" meaning "straight" and "rna" for "ribonucleic acid," reflecting the linear nature of their RNA genomes.

Classification

Orthornavirae is divided into several phyla based on the type of RNA genome and the replication strategy:

• Kitrinoviricota: This phylum includes positive-sense single-stranded RNA viruses. Members of this phylum are known for their ability to directly translate their RNA genome into proteins upon infection of a host cell.

• Lenarviricota: This phylum consists of positive-sense single-stranded RNA viruses that infect plants and fungi. They are characterized by their unique replication mechanisms and host interactions.

• Pisuviricota: This phylum includes a diverse group of positive-sense single-stranded RNA viruses, many of which infect animals and plants. They are known for their complex life cycles and interactions with host organisms.

• Duplornaviricota: This phylum comprises double-stranded RNA viruses. These viruses have a segmented genome and are known for their ability to infect a wide range of hosts, including humans, animals, and plants.

• Negarnaviricota: This phylum includes negative-sense single-stranded RNA viruses. These viruses must first transcribe their RNA genome into a positive-sense RNA before translation can occur. They are known for causing significant diseases in humans and animals, such as influenza and rabies.

Replication

The replication of Orthornavirae viruses involves the synthesis of RNA from an RNA template, a process catalyzed by the viral RNA-dependent RNA polymerase. This enzyme is crucial for the replication cycle of these viruses, allowing them to produce new viral genomes and mRNA for protein synthesis.

Pathogenesis

Orthornavirae includes many viruses that are pathogenic to humans, animals, and plants. The mechanisms of pathogenesis vary widely among different viruses, but common strategies include evasion of the host immune response, manipulation of host cell machinery, and induction of cell death.

Evolution

The evolution of Orthornavirae is driven by high mutation rates due to the lack of proofreading mechanisms in RNA-dependent RNA polymerases. This leads to rapid genetic diversity and adaptation, allowing these viruses to quickly evolve resistance to antiviral drugs and vaccines.

Also see

• Riboviria
• RNA virus
• Virus classification
• Viral replication
• Viral pathogenesis

Virus classification

Diagram of a virus structure

• 
  MBio.02329-18.F1.large
• 
  Lassa virus
• 
  Lymphocytic choriomeningitis virus
• 
  Sin Nombre virus Hanta TEM
• 
  Marburg virus
• 
  Ebola virions
• 
  Influenza virus particle
• 
  Measles virus
• 
  Mumps virus, negative stained TEM