There are two types of herpes simplex virus, HSV-1 and HSV-2. These viruses are very similar in many ways, and both can cause either oral herpes or genital herpes. They do, however, prefer to live in different areas, and they follow different patterns of reactivation. For this reason, it's useful to find out which type you have, by asking your health care provider to request this information from the lab test that is done to diagnose your herpes.
Under a microscope, HSV- 1 and 2 are virtually identical, sharing approximately 50% of their DNA. Both types infect the body's mucosal surfaces, usually the mouth or genitals, and then establish latency in the nervous system. For both types, at least two-thirds of infected people have no symptoms, or symptoms too mild to notice. However, both types can recur and spread even when no symptoms are present.
The primary difference between HSV-1 and HSV-2 are where they tend to establish latency. HSV-1 tends to live in a collection of nerves near the ear. From there it tends to recur on the lip or face. HSV-2 likes a collection of nerves at the base of the spine and tends to recur in the genital area. Even this difference is not absolute either type can reside in either or both parts of the body and infect oral and/or genital areas. Unfortunately, many people aren't aware of this, which contributes both to the spread of type 1 and to the misperception that the two types are fundamentally different.
HSV-1 causes about 1/3 of new genital infections, and the vast majority of oral infections, which cause cold sores. About 60% of the US population over the age of 12 is infected with HSV-1 virus. If your first episode is caused by HSV-1, there is a 50% to 60% chance you will have a recurrence in the first year. In the case of oral HSV-1, many of the approximately 100 million Americans who are infected acquired the virus when they were children. By the time they're adults, only some 5% of people are bothered enough to consider oral HSV-1 a medical problem.
HSV-2 accounts for about 2/3 of new genital infection, but is responsible for 90-95% of recurrences. About 90% of those who have HSV-2 infection do not know that they are infected. It's rare to find someone who has oral HSV-2, but it can happen. After recovery from a possible first episode, such an infection is of little consequence in most cases, since oral HSV-2 is not likely to reactivate and cause signs or symptoms. Almost all of the approximately 40 million Americans infected with HSV-2 acquired the virus as teenagers or adults. In the first year, those who have recurring outbreaks experience an average of four to six episodes. Over time, as with oral infections, the number of outbreaks usually drops off.
The common myth is that HSV-1 causes a mild infection that is occasionally bothersome, but never dangerous. The reality? HSV-1 is usually mild, especially when it infects the lips, face, or genitals. However, in some cases type 1 can recur spontaneously in the eye, causing ocular herpes, a potentially serious infection that can lead to blindness. In very rare cases, HSV- 1 can spread spontaneously to the brain, causing herpes encephalitis, a dangerous infection that can lead to death.
If you have a positive result on your herpes culture and a negative result on a type specific herpes antibody test (a blood test for herpes) then that means that your body has not had a chance to build up antibodies, which means that you probably caught herpes from your most recent partner. If you have more than one partner you may have difficulty knowing who you contracted your herpes from. And if you have had more than one partner in your lifetime, and both the culture and the blood test come back positive for herpes, then you may never know who you contracted herpes from.
While HSV can be a frustrating and painful condition for some people, in general the virus is less a medical problem than a social problem. For most of us, genital herpes is no more dangerous than a cold sore.