HSV is spread by contact, as the virus is shed in saliva, tears, genital and other secretions.
By far the most common form of infection results from a kiss given to a child or adult from a person shedding the virus.
Primary infection is usually trivial or subclinical in most individuals. It is a disease mainly of very young children ie. those below 5 years.
There are 2 peaks of incidence, the first at 0 - 5 years and the second in the late teens, when sexual activity commences.
About 10% of the population acquires HSV infection through the genital route and the risk is concentrated in young adulthood.