It's better to know everything about herpes transmission to avoid this rather unpleasant disease. The first thing to remember is that HSV can't be passed to a person through air. The virus only gets to a person's body after skin to skin contact. For example, if a person already has herpes and kisses another person in lips then the disease passes to a healthy one. If a person who has oral HSV touches partner's genitals, then the virus transfers to a healthy person in the form of genital herpes too.
HSV transmission is a very quick process. That's why you have to be very careful with your partners and both control your hygiene (oral and genital).
Some people think that HSV transmission can only happen when the sore is present. But it's a wrong thought. There were reported some cases when the reddishness was experienced, some itching and tingling on the skin area, and after the clinical researches doctors made a conclusion about the presence of the herpes virus. So you have to control your skin every day. And if you notice even the smallest possible symptoms of herpes, you have to visit doctor immediately and tell him about your worries and doubts to avoid HSV transmission. That's why it's not recommended to have any oral, anal or vaginal contact until those symptoms pass away and you heal herpes outbreak.
You should know that herpes transmission can take place even when an ill person doesn't have any HSV symptoms or an outbreak at the moment. Some people may "shelter" the virus for a while in their body and not even know that they have it. In some cases herpes symptoms are so weak that any doubts and suspicions can appear. But when infected people have contact with healthy people, HSV transmission definitely happens. We know about few exceptions when herpes transmission didn't take place though one of the partners was infected. But those cases are too rare to be considered a rule.
HSV transmission doesn't mean that the virus is passed from one person to another only. Virus transmission can even happen when a person touches his or her own outbreaks and then spreads the virus all around his or her body. For example you touch sores when they are in their active phase and then you touch your eyes or other parts of the body. As the result you might get herpes on your fingers, eyes or anywhere else on your body, where the contact took place.
HSV transmission is very dangerous when a pregnant woman is ready to born her child. That's why pregnant women have to be very careful and consult their doctor all the time during a pregnancy.