Rabies virus particles (Negri body, yellow) inside neuron, computer illustration. Rabies viruses multiply inside the cytoplasm of nerve cells (neurons). Their accumulation is seen histologically as so-called Negri bodies. The presence of Negri bodies inside a tissue sample from the central nervous system is used to diagnose rabies. The rabies virus (order Mononegavirales) is transmitted to humans from the bite of an infected animal. The virus infects the central nervous system, causing encephalopathy and ultimately death. Symptoms include fever, breathing difficulties, muscle spasms, and hydrophobia.