Lyssaviruses

Lyssaviruses are a genus of enveloped, bullet-shaped, negative-sense RNA viruses in the family Rhabdoviridae. The prototypic member is the classical rabies virus. The genus includes several species such as Rabies lyssavirus, Lagos bat lyssavirus, Mokola virus, Duvenhage virus, European bat lyssaviruses 1 and 2, and Australian bat lyssavirus.

Genome and structure: The genome is a single negative-sense RNA about 11 kilobases long and encodes five proteins: nucleoprotein (N), phosphoprotein (P), matrix (M), glycoprotein (G), and the large RNA-dependent RNA polymerase (L). The virion is enveloped and bullet-shaped. Lyssaviruses are neurotropic and enter the body at the site of a bite or mucosal exposure; replication occurs in local tissue before spread to peripheral nerves and the central nervous system.

Transmission and disease: Classic rabies cycles involve dogs and other mammals as reservoirs; many lyssaviruses are associated with bats. Transmission mainly occurs through saliva in bites, though rare aerosol exposure has been reported in caves. After infection, incubation is variable. Clinical disease includes furious rabies and paralytic rabies, with encephalitis as a hallmark and almost always fatal once symptoms develop.

Diagnosis, prevention, and public health: Diagnosis relies on antigen or RNA detection in brain tissue or saliva; post-mortem testing with direct fluorescent antibody is common, while antemortem RT-PCR can aid in surveillance. Prevention includes pre-exposure vaccination for high-risk groups and post-exposure prophylaxis consisting of wound cleaning, rabies vaccine, and, when indicated, rabies immunoglobulin. Control in dogs and wildlife reservoirs reduces human cases; vaccines show variable cross-protection against non-rabies lyssaviruses.