: a panoramic view in human infections;
Another mode of virus infection is the latent phase, where the virus is ‘quiescent’ (a state in which the virus is not replicating). A combination of these stages, where virus replication involves stages of both silent and productive infection without rapidly killing or even producing excessive damage to the host cells, falls under the umbrella of a persistent infection. Reactivation is the process by which a latent virus switches to a lytic phase of replication. Reactivation may be provoked by a combination of external and/or internal cellular stimuli.
The focus of the article is on those viruses known to cause latent infections, which include herpes simplex virus, varicella zoster virus, Epstein–Barr virus, human cytomegalovirus, human herpesvirus 6, human herpesvirus 7, Kaposi’s sarcoma-associated herpesvirus, JC virus, BK virus, parvovirus and adenovirus.
The ability to move back and forth from latent to lytic infections helps the virus spread from infected individuals to uninfected individuals. Apart from these two phases, a few viruses also have yet another method of replication, termed ‘persistent infection’. Persistent viruses (e.g., hepatitis B virus) are those that are not eliminated following primary infection and remain in specific cells of the infected individuals. An infected individual experiences a persistent infection in which the virus is capable of replicating slowly, silently or at low levels without causing excessive damage to the host cell.
Viral reactivation is associated with several stress factors , including viral infection (with other viruses), nerve trauma, physiologic and physical changes (e.g., fever, menstruation and exposure to sunlight) and immunosuppression (as in cytomegalovirus [CMV] disease)