Viruses

A virus is a particle composed of at least nucleic acids and proteins that is capable of entering a host cell and causing the production of progeny viruses by damaging that cell. The term virus includes the infectious properties of a virion.

Viruses consist only of a protein coat (capsid), nucleic acids and possibly an envelope (enveloped viruses). The genomic nucleic acids contain the genetic information (see virus classification below).

Viruses do not have their own metabolism, they cannot grow and therefore require living cells in order to reproduce. To do this, they penetrate the cells with their nucleic acids, which are present as DNA or RNA, and alter the normal cell metabolism in such a way that the cell forms new viruses. The affected cells are called host cells. They usually perish as a result of the viral infection.

Fours are only 8 to 800 nm in size, making them much smaller than bacteria. Viruses always contain only one type of nucleic acid (DNA or RNA). Accordingly, a distinction is made between

DNA viruses

and

RNA viruses.

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