IMMUNOLOGY

Detailed explanation-1: -A virus is a tiny, infectious particle that can reproduce only by infecting a host cell. Viruses “commandeer” the host cell and use its resources to make more viruses, basically reprogramming it to become a virus factory. Because they can’t reproduce by themselves (without a host), viruses are not considered living.

Detailed explanation-2: -Viral entry is the earliest stage of infection in the viral life cycle, as the virus comes into contact with the host cell and introduces viral material into the cell.

Detailed explanation-3: -A cell that is infected by a virus or another type of microorganism.

Detailed explanation-4: -Viruses are host-specific because they only can attach to and infect cells of certain organisms. Cells that a virus may use to replicate are called permissive. The virus attacks the host cell by first attaching to a specific receptor site on the membrane of the host cell.

Detailed explanation-5: -Indeed, viruses have the remarkable ability to spread from one host to another host, hosts that belong to the three cellular domains of life-Archaea, Bacteria, and Eukarya. This constitutes their host range.