Herpes type 1 is the strain of herpes simplex virus that is usually responsible for the development of cold sores. In contrast, herpes type 2 is the type which normally causes genital herpes symptoms. This is not always the case, however, and herpes type 1 can sometimes cause genital herpes sores, depending on the method of transmission. Type 1 herpes can also cause infection in areas other than the mouth or genitals, but this is extremely rare.
Herpes is characterized by several things. First, herpes infection cannot be cured. When a person is infected with the herpes virus, it is there to stay, because after the infection period the virus infects the nervous system and enters a period of latency. This means the virus continues to replicate in low numbers without causing symptoms. When the virus is latent, it is not infectious and cannot be transmitted to other people.
Another characteristic of herpes type 1 and type 2 is that most people have an asymptomatic infection punctuated by periods in which symptoms develop. Symptoms include the development of sores in either the oral or genital area, with the appearance of the sores usually preceded by a tingling or burning sensation in the affected area. The virus is infectious once symptoms begin to appear.
Most oral cases of herpes, known by most people as cold sores or fever blisters, are caused by the herpes virus. In the US, just under 58% of people are infected with the oral herpes virus, but only around one third ever experience symptoms. It is rare for type 2 to cause oral herpes infection, and people who experience an initial instance of such an infection rarely have a recurrent episode.
While Herpes type 1 most often causes the development of oral symptoms, and occasionally genital symptoms, infectious outbreaks can occur in other parts of the body. The herpes virus can cause infection in the eye, which is potentially serious and can lead to blindness. Even more rarely the infection can spread to the brain, causing encephalitis.
Herpes transmission usually occurs via mouth-to-mouth, mouth-to-genital, or genital-to-genital contact. In the majority of cases, this contact occurs when the person with herpes does not know they have the virus, or when they do know but are not aware they are in an infectious stage. Another important point is that type 1 herpes is the most easily transmitted form of the virus. This is because its preferred site of infection is the oral region, and the type of contact which can transmit the virus is a common form of social greeting.