Viruses are nonliving agents that depend on the host cell that they are infecting to reproduce. They are bundles of genetic material enclosed in a capsid (some viruses have an additional layer called the viral envelop). Viruses can only thrive and replicate inside the environment of a living cell of other organisms. Viruses adapt to the environment (the cell) they are in by infecting the entire cell. Viruses can infect other nearby cells by infecting its genetic code (either DNA or RNA) and spread. Viruses develop and spread by attaching its protein tail to a receptor site on the host cell wall and injecting its genetic material into the host cell. The virus can then take over the cell and spread to infect other cells in a similar way. This is how viruses replicate. Outside of the host cell, most viruses are inert.
