| Banna virus | |
|---|---|
 | |
| Electron micrograph of Banna virus | |
Virus classification | |
| (unranked): | Virus |
| Realm: | Riboviria |
| Kingdom: | Orthornavirae |
| Phylum: | Duplornaviricota |
| Class: | Resentoviricetes |
| Order: | Reovirales |
| Family: | Sedoreoviridae |
| Genus: | Seadornavirus |
| Species: | Banna virus |
Banna virus (BAV) is a virus belonging toReoviridae, a family of segmented, non-enveloped,double-stranded RNA viruses.[1] It is anarbovirus, being primarily transmitted to humans from the bite of infected mosquitoes of the genusCulex.[2] Pigs and cattle have also been shown to become infected.[3] The most common symptom of infection isfever, but in some casesencephalitis may occur.[4] There is no specific treatment for infection, so treatment is aimed at alleviating the severity of symptoms until the immune system has cleared the infection.
BAV is a small (72–75 nm in size), non-enveloped, double-stranded RNA virus surrounded by anicosahedral protein coat. Fibre proteins extend outward from the surface of the protein coat. Thegenome of BAV is about 19,500 base pairs in length, linear and segmented into 12 parts, encoding for genes VP1-12. Seven of these, VP1-4 and VP8-10, are structural proteins. VP4 and VP9 form the outer protein coat. The inner particles of the coat are composed of VP1-3, VP8 and VP10. VP7 serves as aprotein kinase, VP1 as anRNA-dependent RNA polymerase, VP3 as acapping enzyme, and VP12 as adsRNA-binding protein.[5][6][7]
Rotaviruses share many physical and genetic characteristics with BAV, indicating a close genetic relation between the viruses.[8] Phylogenetic analysis of the various BAV strains suggests that the BAV-Ch and BAV-In6969 strains were two individualgenotypes at one point in time (A and B), before becoming the prototype species for two distinctserotypes (A and B) among all 38 identified strains.[4]
Clinical features of BAV infection are non-specific and resemble other arboviral encephalitides, so laboratory diagnosis is required to identify BAV as the cause of illness. Detection of the nucleic acid of BAV can be performed with aTaqManreverse transcription polymerase chain reaction (RT-PCR)assay by extracting RNA strands from a sample and reverse transcribing them into detectablecDNA.[9] A recombinant VP9-basedenzyme-linked immunosorbent assay (ELISA) can also be used to identify antibodies to BAV in blood serum and study the seroprevalence of BAV infection in a population.[10]
Banna virus was first isolated from thecerebrospinal fluid of encephalitis patients inXishuangbanna,Yunnan province,People's Republic of China in 1987. Subsequent identification came in theXinjiang province and the virus has since been found elsewhere in China,Indonesia, andVietnam in mosquito populations.[2][5] Because BAV displays similar symptoms toJapanese encephalitis virus (JEV) infection and the two viruses share their method of transmission and geographic distribution, it is possible that some past outbreaks attributed to JEV may have instead been caused by BAV.[3]