Thanks for your question. It is the Herpes Simplex Virus which causes oral and genital herpes. They are of two kinds- Type 1 and type 2. If you are having an outbreak of herpes, there will be some active blisters or cold sores in your genitals or facial areas. Moreover it will last for about 2-3 weeks from the onset of outbreak. After this is suppressed, there will be no further visible lesions or blisters. Herpes simplex virus is simply transmitted to others through skin to skin contact with the cold sore or fever blisters, which are caused by herpes virus. Even if they are categorized by the primary areas which they infect, they can infect in other areas also. That is, oral herpes virus can infect genitals through oral sex and genital herpes virus or type 2 HSV can infect oral areas also. So, the only way to prevent spread of the virus is to avoid oro genital sexual contacts or even skin contacts with the infected person. Hope my answer helps. Take care.