Bwamba Fever

Bwamba Fever
Virus classification
Group: Group V ((-)ssRNA)
Order: Unassigned
Family: Bunyaviridae
Genus: Orthobunyavirus
Species: Bwamba virus

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 segmented RNAs 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 100 nm 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 virus is transmitted to humans through mosquito bites and causes Bwamba fever. The main anthropophilic vectors are Anopheles gambiae and Anopheles funestus.[1] Bwamba fever presents itself as a severe generalised infection of short duration, usually only lasting four to five days. Symptoms include fever, headache, arthralgia, and local as well as generalised pain. "Exanthem is nearly always present and is frequently associated with meningeal involvement. [...] Intestinal tract involvement, especially diarrhea, is also seen. Some patients may also develop a body rash",[1] as reported by the Uganda Virus Research Institute, who also discovered the disease in the 1940s.[2][3] Bwamba fever is present in large parts of Africa and antibodies of the virus have been found ‘as far south as the Republic of South Africa and as far north westwards as Gambia’.[1] Furthermore, Bwamba fever is endemic in several African countries, including Mozambique, Tanzania and Uganda, where the virus was initially discovered.[1] However, the distribution of the virus tends to be underestimated because the symptoms are relatively mild and are often mistaken for malaria.

References

  1. ↑ 1.0 1.1 1.2 1.3 Lutwama, Julius; Rwaguma, Elly; Nawanga, Peter; Mukuye, Anthony (2002). "Isolations of Bwamba virus from south central Uganda and north eastern Tanzania". African Health Sciences 2 (1): 24–28. PMC 2141559. PMID 12789111.
  2. ↑ "The Rockefeller Foundation: Annual Report 1949". The Rockefeller Foundation. Retrieved 17 February 2012. ‘Nine strains, all from human beings and all identical with each other, were designated Bwamba fever virus. [...] Bwamba fever virus [is] believed to be hitherto unknown.’
  3. ↑ "Twentieth Century Africa" The Rockefeller Archive Center. Retrieved 17 February 2012. ‘Among the many viruses and fevers that [Kenneth Smithburn] researched are [...] Bwamba Fever Virus (1939-1943)’

Literature