Herpes develops after you have been infected with the herpes simplex virus (often abbreviated to HSV). There are two types of herpes, HSV-1 and HSV-2. Both types can result in oral herpes or genital herpes.
Herpes is extremely common and results in painful blisters or cold sores. About 67 per cent of the world population under the age of 50 has HSV-1. Most infected people never have visible symptoms such as cold sores, some have cold sores once in their lifetime, while others can get it several times.
The virus can be passed on through saliva, the skin and mucous membranes. The chance of infection is slight if there are no blisters or cold sores, but it is possible to have such mild symptoms that you can be infectious without knowing it.
Most people with oral herpes get infected in childhood when they share food and drink with parents or other children, as the virus can be passed on by saliva. Both HSV-1 and HSV-2 can be passed on through saliva. Cold sores are a sign that you have the infection in the mouth.
The virus is passed on by skin or mucous membrane contact, and so can be transmitted during sexual intercourse, oral sex and anal sex. Both HSV-1 and HSV-2 can infect the genital area. Herpes in the genital area is called genital herpes. Using a condom reduces the risk of infection, but there is still a slight risk as you can be infected in areas not covered by the condom.