Notes on Genus: Phlebovirus

enveloped spheres
enveloped spheres

Type member: Rift Valley fever virus


General Description

This is one of the four animal virus genera in the family Bunyaviridae and is characterised by its ambisense coding strategy of the N and NSs genes on the S segment. The name refers to the phlebotomine vectors of the sandfly fever group of viruses.


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.6400 nt), M (3200-4200 nt) and S (c.1700-1900 nt).

Genus Genomic Organization

Translation of the RNAs produces a polymerase (RNA-L; complementary sense), a protein precursor which is cleaved into two glycoproteins (RNA-M; complementary sense), and two proteins from RNA-S, the coat protein in the complementary sense and a non-structural protein in the virion sense.

Type Member Genomic Organization

The translation strategy is:
  1. RNA-L produces a single protein (L) of 243.6 kDa (RNA polymerase) in the complementary sense
  2. RNA-M produces a protein precursor of 132.0 kDa in the complementary sense, from which two proteins are generated:
    • Glycoprotein G1 (56.5 kDa)
    • Glycoprotein G2 (58.8 kDa)
  3. RNA-S produces the N (nucleocapsid, or coat protein) protein of 27.4 kDa in the complementary sense and
  4. a non-structural protein NSs of 29.9 kda in the virion sense