Bwamba Fever

Bwamba Fever virus is from the genus Orthobunyavirus and belongs to the order Bunyaviridae. It has a negative sense single stranded RNA (ssRNA) genome, and so is classified as a class V virus under the Baltimore classification system. The genome is segmented into three pieces, Large (L), Medium (M) and Small (S), which have a combined length of approximately 12,000nt. The S RNA encodes a nucleocapsid and non structural proteins, the M RNA encodes envelope glycoproteins and a non structural membrane polypeptide and the L RNA encodes an RNA dependent RNA polymerase.

Virus Structure
The segemented RNA’s are surrounded by nucleocapsid proteins that form a Ribonucleoprotein complex, that associates with RNA dependent RNA polymerase. The complex is surrounded by a lipid layer, into which the nuclear complex interacts. Finally the particle is membrane bound, spherical, and in total is approximately 100nm in diameter.

Gene expression and Genome replication
Once inside a host cell cytoplasm, the genomic RNA’s are transcribed into mRNA’s by the associated RNA polymerase. From these transcripts, the host machinery is used for translation into viral proteins. The S segment is slightly different from the rest as it is ambisense, meaning genes run in both the positive and negative directions. To enable correct translation of the proteins, a second round of transcription has to occur.

To replicate the genome, transcription occurs to produce a replicative intermediate, which is then itself transcribed into new RNA genomes, with the aid of the RNA polymerases produced from the gene expression.

Bwamba Fever
Bwamba fever virus is transmitted from vertebrate to vertebrate through a mosquito vector, Anopheles funestus, and causes Bwamba fever. The fever is often mistaken for malaria, and was only identified in the later 1990’s and is believed to be endemic in east Africa, especially Kenya, Tanzania and Uganda, where the virus was first identified by the Uganda Virus Research Institute. There is no specific treatment for the virus, as it causes only a mild fever.