Virus causing rabies in man is: March 2005

Ans. B: Street virus The rabies virus is the type species of the Lyssavirus genus, which encompasses other similar viruses. Lyssaviruses have helical symmetry, with a length of about 180 nm and a cross-sectional diameter of about 75 nm. 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: nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G) and the viral RNA polymerase (L). From the point of entry, the virus is neurotropic, traveling quickly along the neural pathways into the central nervous system (CNS), and then fuher into other organs. The salivary glands receive high concentrations of the virus thus allowing fuher transmission. The virus recovered from naturally occurring cases of rabies is called street virus and is pathogenic for all mammals and shows a long variable incubation period (20-60 days in dogs).