Rabies virus

Rabies virus (Lyssavirus rabies) is a neurotropic virus that causes rabies in animals, including humans. It can cause violence, hydrophobia, and fever. Rabies transmission often occurs through the saliva of animals and less commonly through contact with human saliva. Rabies virus, like many rhabdoviruses, has an extremely wide host range. In the wild it has been found infecting many mammalian species, while in the laboratory it has been found that birds can be infected, as well as cell cultures from mammals, birds, reptiles and insects. Rabies is reported in more than 150 countries and on all continents except Antarctica. The main burden of disease is reported in Asia and Africa, but some cases have been reported also in Europe in the past 10 years, especially in returning travellers.

Rabies virus has a cylindrical morphology and is a member of the Lyssavirusgenus of the Rhabdoviridae family. These viruses are enveloped and have a single stranded RNA genome with negative-sense. The genetic information is packaged as a ribonucleoprotein complex in which RNA is tightly bound by the viral nucleoprotein. The RNA genome of the virus encodes five genes whose order is highly conserved. These genes code for nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G) and the viral RNA polymerase (L). The complete genome sequences range from 11,615 to 11,966 nt in length.

Rabies lyssavirus has a "negative polarity" (or is a negative-sense RNA virus 3'-5'), which means that its genetic material cannot be directly translated into proteins by the host cell's machinery. Once inside the cytoplasm of a cell, the viral polymerase uses the negative strand as a template to create positive-sense messenger RNA (mRNA) strands. These mRNAs are then translated by the host cell to make proteins, and later to replicate the viral genome. All transcription and replication events take place in the cytoplasm inside a specialized "virus factory", the Negri body (named after Adelchi Negri). These are 2–10 μm in diameter and are typical for a rabies infection and thus have been used as definite histological proof of such infection.