Orthomyxoviridae

Orthomyxoviridae is a family of RNA viruses that includes five genera: Influenzavirus A, Influenzavirus B, Influenzavirus C, Isavirus, and Thogotovirus. The viruses in this family are characterized by an enveloped virion that measures approximately 100 nanometers in diameter and a segmented genome.

Structure and Genome

The viruses in the Orthomyxoviridae family are enveloped, with a spherical or filamentous shape. The envelope of the virus is derived from the host cell membrane, and contains two major glycoproteins, hemagglutinin (H) and neuraminidase (N). These proteins play a crucial role in the virus's ability to infect host cells.

The genome of Orthomyxoviridae viruses is made up of segmented, negative-sense, single-stranded RNA. This segmented nature of the genome allows for the exchange of gene segments, a process known as genetic reassortment. This is a major factor in the emergence of new strains of influenza viruses.

Replication

Orthomyxoviridae viruses replicate in the nucleus of the host cell, a unique feature among RNA viruses. The replication process involves the transcription of the viral RNA into complementary RNA (cRNA), which is then used as a template for the production of viral RNA.

Pathogenesis and Immunity

Viruses in the Orthomyxoviridae family are responsible for a wide range of diseases in humans and animals. The most well-known of these is influenza, caused by Influenzavirus A and B. Influenza is a highly contagious respiratory illness that can cause severe illness and death, particularly in high-risk populations.

Immunity to Orthomyxoviridae viruses is primarily mediated by the immune system's response to the H and N glycoproteins on the surface of the virus. However, the high rate of mutation in these proteins, a process known as antigenic drift, allows the virus to evade the immune response, leading to recurrent epidemics.

See Also

• Influenza virus
• Influenza pandemic
• Antigenic drift
• Antigenic shift