Herpes simplex is caused by Herpes virus hominis, of which there are two distinct serologic types designated as HSV-1 and HSV-2. The first mainly causes disease above the waist, such as cold sores; the second most commonly causes disease below the waist, especially genital herpes. Exceptions to this generalization occur especially among the newborn. The initial active phase is followed by prolonged latency. But the virus can be reactivated by another infection, stress, exposure to sunshine, or any number of other bodily changes.

Etiology and Epidemiology

The herpes viruses are visible in infected cells by electron microscopy and may be grown in the chick embryo, in tissue cultures, and in laboratory animals that react differently to types HSV-1 and HSV-2.

HSV-1 is shed from cells in the lacrimal and salivary glands, and both types are shed from the primary and recurrent lesions of the mucous membranes and skin. Samples of infected adults show that 2 to 4 percent are excreting the virus at a given time.

Infection with the herpes simplex virus results from person-to-person contact. HSV-1 infections commonly are transmitted by oral secretions through kissing or the sharing of eating utensils, and thus herpetic infection can easily be spread within a family. Normally HSV-1 infections are painful and bothersome but have no serious consequences. An exception can be when the virus invades the cornea of the eye. Conjunctival or corneal herpes may produce scars that impair vision. It may occur among wrestlers from skin-to-skin contact. Another form of HSV-1 infection, called herpetic paronychia, may occur in dentists and in hospital personnel.