An Ecological Framework of the Human Virome Provides Classification of Current Knowledge and Identifies Areas of Forthcoming Discovery

Parker, Michael T.

While the virus has a safe home during persistence, the question arises that if a virus is not replicating, or is present at very low levels, how is it transmitted to the next host? The answer lies in the spread of virus via close intrahost interactions that may occur many times during the host's life. The most conventional method by which persistent viruses are transmitted is contact between mucous membranes. This includes kissing and sexual intercourse, but can also include transmission vertically from mother to child, in rare cases [37] . The prototypical example is herpes simplex virus 1 (HSV-1) which, after an initial acute or subclinical infection, moves into a sensory neuron and enters a period of latency [52] . Later in life the virus can break latency, move down the neuron to the skin, and begin to replicate, the prototypical presentation of which is a cold sore. These lesions release infectious virus that can be transmitted to a new host. After a short time, the virus returns to latency and the lesion will heal [52] . The success of this strategy of latency and mild pathogenic effect is made obvious by the fact that approximately two-thirds of the world's population is infected with HSV-1 [53] .