Basics of virology.

Viruses are important pathogens of the nervous system. Here we describe the basic properties of viruses and the principles of virus classification, evolution, structure, and replication, with a focus on neurotropic viruses that are important neuropathogens of humans. These properties then provide the background for introductions to pathogenesis of viral diseases of the nervous system, host immune responses to virus infection, and the diagnosis and treatment of virus infections of the nervous system.