Notes on Genus: Orthobunyavirus

enveloped spheres
enveloped spheres

Type member: Bunyamwera virus


General Description

This is one of the four animal virus genera in the family Bunyaviridae. The N and NSs proteins are encoded from overlapping reading frames from the S segment which, at less than 1.1 kb, is smaller than those of any of the other genera in the family. The name is derived from the type member, originally isolated from Bunyamwera, in Uganda.


Virions pleomorphic in shape and size, spheroidal and enveloped, 80-110 nm in diameter. 3 filamentous nucleocapsids per envelope, each 200-3000 nm long (depending on arrangement) and 2-2.5 nm in diameter. Symmetry helical.

Virions composed of 1-2 % nucleic acid, over 50 % protein and 20-30 % lipid.


Linear, tripartite negative sense ssRNA: L (c.7000 nt), M (c.4500 nt) and S (c.980 nt).

Genus Genomic Organization

Translation of the RNAs produces a polymerase (RNA-L), a protein precursor which is cleaved into two glycoproteins and a non structural protein (RNA-M), and two proteins from RNA-S, the coat protein and a non-structural protein in an overlapping reading frame.

Type Member Genomic Organization

All the RNAs are translated from the complementary strand:
  1. RNA-L produces a single protein (L) of 258.7 kDa (RNA polymerase)
  2. RNA-M produces a protein precursor of 162.1 kDa, from which three proteins are generated:
    • Glycoprotein G1 (108.7 kDa)
    • Non-structural protein NSm (19.5 kDa)
    • Glycoprotein G2 (33.8 kDa)
  3. RNA-S produces the N (nucleocapsid, or coat protein) protein of 26.5 kDa and
  4. (from an overlapping reading frame) a non-structural protein NSs of 11.1 kda