Principles and Practice of Clinical Virology, 4th Edition

Virology is that branch of microbiology concerned with viruses and diseases. These groups of minute infectious agents are, with certain exceptions (e.g., poxviruses) lack an independent metabolism and replicate only within living host cells. Like living organisms, they reproduce with genetic continuity and also mutate. Normally classified into three subgroups on the basis of host specificity (bacterial viruses, animal viruses, and plant viruses), they are also classified by origin, mode of transmission, symptoms produced, and where first located.