Virus Infection

Viruses are obligate intracellular parasites that can exist as potentially active but inert entities outside of cells. While there are viruses that infect many animal, plant, and protist cells and result in effects on the host that range from inapparent infection to lethality, all virus infections have some features in common. These include an entry phase, an intracellular phase consisting of multiplication, integration, or latency formation, a virus release phase, and usually some sort of host responses to the presence of the virus infection. It is often these host responses that appear as the most prominent signs and symptoms of virus infection.