Rabies virus

Description and significance
The Rabies virus is a member of the order, Mononegavirales, which encompasses viruses containing non-segmented, negative-stranded RNA genomes. The term originates from the Latin, “rabies,” which means “madness.” This may have been derived from the Sanskrit word, rabhas, “to do violence.” The virus has a distinct “bullet” shape, placing it in the Rhabdoviridae family, which includes at least three genera of viruses that infect animals, such as Lyssavirus, Ephemerovirus, and Vesiculovirus. The rabies virus belongs to the Lyssavirus genus (Greek word, lyssa, is derived from “lud” or “violent.”) which also includes the Aravan virus, Australian bat Lyssavirus, Duvenhage virus, European bat virus 1 and 2, Lagos bat virus, and Mokola virus. Lyssaviruses have helical symmetry and are about 180 nm in length, with a cross-sectional diameter of 75 nm. The most prevalent strain of rabies is Rabies Virus (RABV; genotype 1), which is the type that infects both bats in the Americas and terrestrial animals throughout the world. Rabies is a zoonotic disease, meaning it is transmitted from animals to humans. The virus infects domestic and wild animals, and is transmitted to humans through close contact with infected saliva, usually through bites or scratches. This viral, neuroinvasive disease causes acute encephalitis (brain inflammation) in warm-blooded animals. The virus also enters the salivary glands in high concentrations, leading to further transmission. Once the signs and symptoms of the virus arise, there is no treatment and the disease is usually fatal. The disease is prevalent in nearly every continent of the world, with over 55,000 human deaths a year, 95% of which occur in Africa and Asia.

Genome structure
Rabies is an RNA virus. The genome encodes 5 proteins: nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G), and polymerase (L). The genome is non-segmented, linear antisense RNA. RNA-dependent RNA transcriptase and some structural proteins are present in the nucleocapsid.

Virus structure
The virus has a bullet-like shape; one end is rounded while the other is planar or concave. The virus’s lipoprotein envelope contains about 400 spikes on its surface, which are composed of glycoprotein (G). Within the envelope lies the membrane or matrix (M) protein layer, which may be invaginated at the planar end. The Glycoprotein spikes do not cover the planar end. The virion’s core consists of helically arranged ribonucleoprotein, which consists of protein and RNA.