Virion Structure of a Orthomyxoviridae

The virions of an orthomyxovirus consist of:

1. An envelope
2. A matrix protein
3. A nucleoprotein complex
4. A nucleocapsid
5. A polymerase complex.

• The virus capsid is enveloped.
• The virions can be in spherical, pleomorphic or filamentous forms.
• They are 80-120 nm in diameter and 200-300 nm long.
• The surface projections are densely dispersed, hemagglitinin-esterase (HEF) spikes, or spaced widely apart, hemagglutinin (HA) spikes.
• There are about 500 spikes evenly dispersed or clustered and are covering the surface comprising hemagglutinin, neuraminidase, or esterase-esterase.
• The surface projections are composed of one or different types of proteins and are 10-14 nm long and 4-6 nm in diameter.

The nucleocapsid is elongated with helical symmetry and is segmented with loops at one end.

Picture extracted from: http://pathmicro.med.sc.edu/mhunt/RNA14.jpg