A virus is a tiny infectious agent that is usually regarded as a nonliving, but extremely complex, group of molecules that reproduces inside the cells of living hosts. When infected, the host cell is forced to rapidly produce thousands of identical copies of the original virus. Unlike most living things, viruses do not have cells that divide; new viruses assemble in the infected host cell and can cause various diseases that may result in serious illness and possible death in humans, animals, and plants.
A virus is a tiny infectious agent that is usually regarded as a nonliving, but extremely complex, group of molecules that reproduces inside the cells of living hosts. When infected, the host cell is forced to rapidly produce thousands of identical copies of the original virus. Unlike most living things, viruses do not have cells that divide; new viruses assemble in the infected host cell and can cause various diseases that may result in serious illness and possible death in humans, animals, and plants.