Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 19

Viruses are microscopic infectious agents that can reproduce only inside a cell that they infect: they are obligate parasites of their host cells. Viruses spread from cell to cell via infectious particles called virions, which contain genomes comprising RNA or DNA surrounded by a protective protein coat. Upon particle entry and disassociation in a host cell, the viral genome directs synthesis of viral components by cellular systems. Progeny virus particles are formed in the infected cell by de novo self-assembly from the newly synthesized components.

As will be discussed in the following chapters, advances in knowledge of the structure of virus particles and the mechanisms by which they are produced in their host cells have been accompanied by increasingly accurate definitions of these unique agents. The earliest pathogenic viruses, distinguished by their small size and dependence on a host organism for reproduction, emphasized the importance of viruses as agents of disease. But there are many other important reasons to study viruses.