Viral latency is a stage in the lifecycle of some pathogenic viruses that may help a virus hide from the host. In latency viruses become dormant, also called latent, in infected cells. These infections are considered persistent but not chronic because viral replication is not occurring. During this time the viral genome is still present. The viral genome may be in one of two forms; genetic episomes, distinct objects that may be in the nucleus or cytoplasm in lariat or linear structures, or as a provirus which is the genome of the virus integrated into the host cell’s genome. Once the virus has entered latency it may need maintenance by the expression of some viral genes. As the cell replicates the daughter cells are already infected and any of the latently infected cells can be stimulated to proceed to lytic infection.
Though a latent virus may at times be reactivated a more serious complication is the transformation of the cell and forcing it into uncontrolled division. Many of the known oncogenic viruses including herpesviradae and HPV are shown to have latent periods. The transformation of the infected cell can be from the effects of the maintenance proteins activating growth receptors. When the viral genes insert into the host DNA it may change the expression of host genes and cause transformation of the cell. Either of these effects increases the replication of infected cells and are beneficial for the virus but may increase the harm done to the host.
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