Orthomyxoviridae: Meaning (information, definition, explanation, facts)

The orthomyxoviridae is a family of RNA viruses which infect vertebrates. It includes those viruses which cause influenza.

Morphology

The virions have envelopes and occur in pleomorphic and filamentous forms. In general the virus's morphology is spherical with particles 50-120 nm in diameter, or filamentous virions 20 nm in diameter and 200-300(-3000) nm long. There are distinct surface projections of envelope, with some 500 spikes, each projecting 10-14 nm from the surface with some types (i.e. hemagglutininesterase (HEF)) dispersed evenly over all the surface, and other types in clusters (i.e. hemagglutinin (HA)).

The major glycoprotein (HA) is interposed irregularly by clusters of neuraminidase (NA), with a ratio of HA to NA of about 4-5 to 1).

The nucleocapsids are enclosed within lipoprotein membranes; nucleoproteins of different size classes with loop at each end; the arrangement within virion uncertain. The nucleocapsids are filamentous and fall in the range of 50-130 nm long and 9-15 nm in diameter. Their symmetry is helical.

Viruses of this family contain 7 segments of to 8 segments of linear negative-sense single stranded RNA.

The total genome length is 12000-15000 nucleotides (nt). The largest segment 2300-2500 nt; of second largest 2300-2500 nt; of third 2200-2300 nt; of fourth 1700-1800 nt; of fifth 1500-1600 nt; of sixth 1400-1500 nt; of seventh 1000-1100 nt; of eighth 800-900 nt. Genome sequence has terminal repeated sequences; repeated at both ends. Terminal repeats at the 5'-end 12-13 nucleotides long. Nucleotide sequences of 3'-terminus identical; the same in genera of same family; most on RNA (segments), or on all RNA species. Terminal repeats at the 3'-end 9-11 nucleotides long. Encapsidated nucleic acid is solely genomic. Each virion may contain defective interfering copies.

See also:

• Virus classification
• Avian influenza