The mechanism of rabies induced-agressive behavior involves viral infection of the limbic system in the brain, wich is responsible for our most primitive behaviors and responses. Rabies virus affects the limbic system while mantaining more superior cerebral cortical centers practically intact, so you most primitive behaviors are affected first and you still remains conscious.

In particular, a study of 1992 inoculated skunks with different strains of rabies virus; one caused agressive behavior, hydrophobia and convulsions, while the other caused paralysis but not behavioral disturbances. When they analysed the brain of these animals, they found that the ones who displayed agressivity, all had viral infection concentrated in the brain-stem, at the base of the brain, a structure vital to control our most automatic and primitive functions. In particular, there are strong viral infection at an area of the brain-stem called midbrain raphe nuclei. The raphe nuclei sends serotonin to all the brain, so it can control the function of various brain areas. Animals with don't showed agressive behavior with rabies had low or none viral infection at these raphe nuclei.

It is supposed that, when rabies virus changes neurons at these raphe nuclei, serotonin control over the brain is changed and this impinge on circuits involved with emotional and motor functions resulting in impulsive behaviors. It's like the defensive responses of the brain to threats is being turned-on in a exagerated way and this results in agressive behavior wich includes bitting others.

Smart NL, Charlton KM (1992) The distribution of challenge virus stan- dard rabies virus versus skunk street rabies virus in the brains of experimentally infected rabid skunks. Acta Neuropathol 84:501– 508

Jackson AC. Diabolical effects of rabies encephalitis. J Neurovirol. 2016 Feb;22(1):8-13.