Banna virus (BAV) is a virus belonging to ''

Reovirales ''Reovirales'' is an Order (biology), order of double-stranded RNA viruses. Member viruses, called reoviruses, have a wide Host (biology), host range, including vertebrates, invertebrates, plants, protists and fungi. They lack lipid Viral envelop ...

'', an order of segmented, non-enveloped, double-stranded RNA viruses. It is an

arbovirus Arbovirus is an informal name for any virus that is Transmission (medicine), transmitted by arthropod Vector (epidemiology), vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo ...

, being primarily transmitted to humans from the bite of infected mosquitoes of the genus '' Culex''. Pigs and cattle have also been shown to become infected. The most common symptom of infection is

fever Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with Human body temperature, body temperature exceeding the normal range caused by an increase in the body's temperature Human body temperature#Fever, s ...

, but in some cases

encephalitis Encephalitis is inflammation of the Human brain, brain. The severity can be variable with symptoms including reduction or alteration in consciousness, aphasia, headache, fever, confusion, a stiff neck, and vomiting. Complications may include se ...

may occur. 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.

Virology

Structure and genome

BAV is a small (72–75 nm in size), non-enveloped, double-stranded RNA virus surrounded by an icosahedral protein coat. Fibre proteins extend outward from the surface of the protein coat. The

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

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 a

protein kinase A protein kinase is a kinase which selectively modifies other proteins by covalently adding phosphates to them ( phosphorylation) as opposed to kinases which modify lipids, carbohydrates, or other molecules. Phosphorylation usually results in a f ...

, VP1 as an

RNA-dependent RNA polymerase RNA-dependent RNA polymerase (RdRp) or RNA replicase is an enzyme that catalyzes the self-replication, replication of RNA from an RNA template. Specifically, it catalyzes synthesis of the RNA strand Complementarity (molecular biology), compleme ...

, VP3 as a capping enzyme, and VP12 as a dsRNA-binding protein.

Types and evolution

Rotavirus Rotaviruses are the most common cause of diarrhea, diarrhoeal disease among infants and young children. Nearly every child in the world is infected with a rotavirus at least once by the age of five. Immunity (medical), Immunity develops with ...

es share many physical and genetic characteristics with BAV, indicating a close genetic relation between the viruses. Phylogenetic analysis of the various BAV strains suggests that the BAV-Ch and BAV-In6969 strains were two individual

genotype The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...

s at one point in time (A and B), before becoming the prototype species for two distinct

serotype A serotype or serovar is a distinct variation within a species of bacteria or virus or among immune cells of different individuals. These microorganisms, viruses, or Cell (biology), cells are classified together based on their shared reactivity ...

s (A and B) among all 38 identified strains.

Diagnosis

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 a TaqMan reverse transcription polymerase chain reaction (RT-PCR)

assay An assay is an investigative (analytic) procedure in laboratory medicine, mining, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity ...

by extracting RNA strands from a sample and reverse transcribing them into detectable cDNA. A recombinant VP9-based enzyme-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.

History

Banna virus was first isolated from the

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

of encephalitis patients in Xishuangbanna, Yunnan province,

People's Republic of China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

in 1987. Subsequent identification came in the Xinjiang province and the virus has since been found elsewhere in China,

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

, and

Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...

in mosquito populations. Because BAV displays similar symptoms to Japanese 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.

References

{{Taxonbar, from=Q16243472 Seadornaviruses