Rabies virus. Coloured scanning electron micro- graph (SEM) of rabies virus particles infecting a mammalian cell. The rod-shaped particles (yellow) consist of a protein shell or capsid enclosed by a lipoprotein envelope. The capsid contains the genetic material, RNA (ribonucleic acid). Rabies virus primarily affects animals but can be transmitted to humans through a break in the skin. It spreads slowly through the peripheral nervous system to the brain, where it causes inflammation resulting in fever and delirium. Infection in humans can be fatal, though modern vaccines are effective if taken within the incubation period of the virus. Magnification unknown.