病毒性感染与细菌感染不同,病毒缺乏完整的酶系统,所以仅能在活细胞中寄生繁殖,从而使机体患病。除狂犬病毒的个别株系和急性海绵状病毒外,中枢神经系统的病毒感染常常是全身感染的并发症。病毒进入中枢神经系统的途径可有三种:一是病毒直接进入神经纤维和神经鞘膜细胞;二是病毒沿呼吸道进入体内,再经血行传播至神经元;三是沿血行传播。虽然有些病毒可同时经由一种以上途径到达神经系统,但血行传播是最常见和最重要的。至于病毒 Viral infections and bacterial infections, the virus lacks a complete enzyme system, it can only live in the parasitic breeding, so that the body sick. In addition to individual strains of rabies virus and acute spongiform encephalomycosis, viral infection of the central nervous system is often a complication of systemic infection. The virus enters the central nervous system can have three ways: First, the virus directly into the nerve fibers and nerve sheath cells; Second, the virus along the respiratory tract into the body, and then spread to the neurons by blood; Third, spread along the bloodstream. Although some viruses reach the nervous system via more than one route simultaneously, blood transmission is the most common and important. As for the virus