http://www.herpes.com/hsv1-2.html
The Truth about HSV-1 and HSV-2
...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 the two viral types is in where they typically establish latency in the body- their "site of preference." HSV-1 usually establishes latency in the trigeminal ganglion, a collection of nerve cells near the ear. From there, it tends to recur on the lower lip or face. HSV-2 usually sets up residence in the sacral ganglion at the base of the spine. From there, it recurs 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.
"People don't understand that you can have type 1 genitally or orally, that the two types are essentially the same virus,' says Marshall Clover, manager of the National Herpes Hotline." One type is associated with stigma, the other is "'just a cold sore"- our society has a euphemism for it so we don't even have to acknowledge that it's herpes.''
...By comparison, HSV-2 is widely believed to be a painful, dangerous infection that affects only people with very active sex lives. The reality? Some 22% of adult Americans from all backgrounds, income levels, and ethnic groups have HSV-2. Like HSV-1, type 2 is usually mild-so mild that two- thirds of infected people don't even know they have it.[/B] Type 2 rarely causes complications or spreads to other parts of the body. It is the most common cause of neonatal herpes, a rare but dangerous infection in newborns; however, type 1 causes up to one-third of neonatal infections.
The two types do behave somewhat differently depending on whether they are residing in their site of preference-the mouth and face for HSV-1, and the genital area for HSV-2. But both types are quite common, and under most circumstances neither is a major health threat. That's one reason medical professionals tend to dismiss HSV -2 despite the emotional trauma a diagnosis can cause for a patient.
...On the other hand, 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.
A third factor influencing the frequency of HSV -1 and 2 outbreaks is whether the virus is established in its site of preference. While HSV can infect both genital and oral areas, both types cause milder infections when they are away from "home" territory. Outside their site of preference, both type 1 and 2 lose most of their punch.
For example, most people infected with HSV-1 in the genital area have few, if any, outbreaks after the initial episode, far fewer than is typical with either oral HSV-1 or genital HSV-2. While experts estimate that some 30% of genital herpes infections in the United States may be caused by HSV-1, only 2- 5% of recurring genital outbreaks are caused by HSV-1. Research conducted by Lawrence Corey, MD, and colleagues at the University of Washington in Seattle shows that genital HSV-2 recurs 10 times more often than genital HSV-1.
Similarly, HSV-2 infection in theoral area-outside its site of preference-very rarely causes problems. First of all, oral, HSV-2 infections are rare, for reasons discussed below. But even when an infection occurs, recurrent outbreaks are uncommon. In one study (Lafferty et al., New England Journal of Medicine, 1987), oral HSV-2 recurred an average of 0.01 times a year in newly infected people. "I've never convincingly seen an oral type 2 recurrence," says Spruance.
...Both viral types are easily transmitted to their site of preference, and can also be spread to other sites. Both are most contagious during active outbreaks, but are often spread through viral shedding when there are no recognizable symptoms. According to Spruance, people with recurrent oral HSV-1 shed virus in their saliva about 5% of the time even when they show no symptoms. In the first year of infection, people with genital HSV-2 shed virus from the genital area about 6-10% of days when they show no symptoms, and less often over time. (Both of these figures reflect shedding as detected by viral culture.)
From here, however, the question of transmissibility gets more complicated. Acquisition of one type is more difficult-though certainly possible-if you already have the other type. This is because either type, contracted orally or genitally, causes the body to produce antibodies, some of which are active against both HSV-1 and 2. This acquired immune response gives some limited protection if the body encounters a second type. When a person with a prior HSV infection does contract the second type, the first episode tends to be less severe than when no prior antibodies are present.
On a practical level, this means oral HSV-1 is often the most easily acquired herpes infection. Usually the first herpes simplex virus that people encounter, oral HSV-1, is typically spread simply by the kind of social kiss that a relative gives a child. Because children have no prior infection with any HSV type, they have no immune defense against the virus.
By the time they're teenagers or young adults, about 50% of Americans have HSV-1 antibodies in their blood. By the time they are over age 50, some 80-90% of Americans have HSV-1 antibodies.
By comparison, almost all HSV-2 is encountered after childhood, when people become sexually active. Those who have a prior infection with HSV-1 have an acquired immune response that lowers - though certainly doesn't eliminate-the risk of acquiring HSV-2. According to one study (Mertz, Annals of Internal Medicine,1992), previous oral HSV-1 infection reduces the acquisition of subsequent HSV-2 infection by 40%.
A prior infection with oral HSV-1 lowers the risk of acquiring genital HSV-1 even further. Studies show that genital HSV-1 infections almost always occur in people who have no prior infection with HSV of either type (Corey, Annals of Internal Medicine, 1983).
In the absence of prior oral infection, however, HSV-1 spreads easily to the genital area, usually through oral sex. In some countries, such as Japan and parts of Great Britain, genital HSV-1 is as common as genital HSV- 2, or more common.
...What does all this mean on a practical level? Let's look at some examples to find out. Say you have genital HSV-1 and your partner has genital HSV-2. If you have unprotected sex, there is a small but real risk that you will get HSV-2, resulting in more outbreaks and more shedding. "We have documented cases where a person acquires HSV-2 after a prior genital HSV- 1 infection," says Wald. "I don't think it happens often, but it does happen."
On the other hand, it's very unlikely that your partner will get genital HSV- 1 from you. "I've never seen a case of a person acquiring HSV-1 on top of HSV-2," says Wald. "It's possible, but it would be unusual."
What if your partner has genital HSV-2 and you perform oral sex on him or her? Will you get HSV- 2 in the mouth? Given the widespread practice of oral sex (some three-quarters of all adults practice it, according to The Social Organization of Sexuality, 1994) and the prevalence of genital HSV-2 infection, you might expect oral HSV-2 to be relatively common. It's not.
According to one study, almost 100% of recognizable HSV-2 infection is genital (Nahmias, Scandinavian Journal of Infectious Diseases Supplement, 1990). One reason is that most adults are already infected with HSV-1 orally, which provides some immunity against infection with HSV 2. Another reason is that oral HSV-2 rarely reactivates, so even if an infection does exist, no one knows.
So far we've been talking about transmission of HSV-1 or 2 from its site of preference. What about transmission from another site? Say you acquire genital HSV-1 through oral sex. Can you spread the virus to a partner through genital sex?
The answer is yes, but probably not as easily as it was spread through oral sex. The main reason is that the virus reactivates and sheds less often outside its site of preference. Only about one quarter of people with genital HSV- 1 shed virus at all in the absence of symptoms, while 55% of people with HSV-2 do (Wald, New England Journal of Medicine, 1995). "Shedding data appear to parallel recurrence data, meaning that people who have a lot of recurrences also have a lot of shedding," says Wald.
..."Talk to a wise friend," suggests Rebecca, a health communication specialist on the National Herpes Hotline. "Join a support group. Find Someone you respect and exchange ideas them. It's always reassuring to see that not everyone lives inside the walls our society builds around sexual issues and realities. "...
The Truth about HSV-1 and HSV-2
...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 the two viral types is in where they typically establish latency in the body- their "site of preference." HSV-1 usually establishes latency in the trigeminal ganglion, a collection of nerve cells near the ear. From there, it tends to recur on the lower lip or face. HSV-2 usually sets up residence in the sacral ganglion at the base of the spine. From there, it recurs 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.
"People don't understand that you can have type 1 genitally or orally, that the two types are essentially the same virus,' says Marshall Clover, manager of the National Herpes Hotline." One type is associated with stigma, the other is "'just a cold sore"- our society has a euphemism for it so we don't even have to acknowledge that it's herpes.''
...By comparison, HSV-2 is widely believed to be a painful, dangerous infection that affects only people with very active sex lives. The reality? Some 22% of adult Americans from all backgrounds, income levels, and ethnic groups have HSV-2. Like HSV-1, type 2 is usually mild-so mild that two- thirds of infected people don't even know they have it.[/B] Type 2 rarely causes complications or spreads to other parts of the body. It is the most common cause of neonatal herpes, a rare but dangerous infection in newborns; however, type 1 causes up to one-third of neonatal infections.
The two types do behave somewhat differently depending on whether they are residing in their site of preference-the mouth and face for HSV-1, and the genital area for HSV-2. But both types are quite common, and under most circumstances neither is a major health threat. That's one reason medical professionals tend to dismiss HSV -2 despite the emotional trauma a diagnosis can cause for a patient.
...On the other hand, 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.
A third factor influencing the frequency of HSV -1 and 2 outbreaks is whether the virus is established in its site of preference. While HSV can infect both genital and oral areas, both types cause milder infections when they are away from "home" territory. Outside their site of preference, both type 1 and 2 lose most of their punch.
For example, most people infected with HSV-1 in the genital area have few, if any, outbreaks after the initial episode, far fewer than is typical with either oral HSV-1 or genital HSV-2. While experts estimate that some 30% of genital herpes infections in the United States may be caused by HSV-1, only 2- 5% of recurring genital outbreaks are caused by HSV-1. Research conducted by Lawrence Corey, MD, and colleagues at the University of Washington in Seattle shows that genital HSV-2 recurs 10 times more often than genital HSV-1.
Similarly, HSV-2 infection in theoral area-outside its site of preference-very rarely causes problems. First of all, oral, HSV-2 infections are rare, for reasons discussed below. But even when an infection occurs, recurrent outbreaks are uncommon. In one study (Lafferty et al., New England Journal of Medicine, 1987), oral HSV-2 recurred an average of 0.01 times a year in newly infected people. "I've never convincingly seen an oral type 2 recurrence," says Spruance.
...Both viral types are easily transmitted to their site of preference, and can also be spread to other sites. Both are most contagious during active outbreaks, but are often spread through viral shedding when there are no recognizable symptoms. According to Spruance, people with recurrent oral HSV-1 shed virus in their saliva about 5% of the time even when they show no symptoms. In the first year of infection, people with genital HSV-2 shed virus from the genital area about 6-10% of days when they show no symptoms, and less often over time. (Both of these figures reflect shedding as detected by viral culture.)
From here, however, the question of transmissibility gets more complicated. Acquisition of one type is more difficult-though certainly possible-if you already have the other type. This is because either type, contracted orally or genitally, causes the body to produce antibodies, some of which are active against both HSV-1 and 2. This acquired immune response gives some limited protection if the body encounters a second type. When a person with a prior HSV infection does contract the second type, the first episode tends to be less severe than when no prior antibodies are present.
On a practical level, this means oral HSV-1 is often the most easily acquired herpes infection. Usually the first herpes simplex virus that people encounter, oral HSV-1, is typically spread simply by the kind of social kiss that a relative gives a child. Because children have no prior infection with any HSV type, they have no immune defense against the virus.
By the time they're teenagers or young adults, about 50% of Americans have HSV-1 antibodies in their blood. By the time they are over age 50, some 80-90% of Americans have HSV-1 antibodies.
By comparison, almost all HSV-2 is encountered after childhood, when people become sexually active. Those who have a prior infection with HSV-1 have an acquired immune response that lowers - though certainly doesn't eliminate-the risk of acquiring HSV-2. According to one study (Mertz, Annals of Internal Medicine,1992), previous oral HSV-1 infection reduces the acquisition of subsequent HSV-2 infection by 40%.
A prior infection with oral HSV-1 lowers the risk of acquiring genital HSV-1 even further. Studies show that genital HSV-1 infections almost always occur in people who have no prior infection with HSV of either type (Corey, Annals of Internal Medicine, 1983).
In the absence of prior oral infection, however, HSV-1 spreads easily to the genital area, usually through oral sex. In some countries, such as Japan and parts of Great Britain, genital HSV-1 is as common as genital HSV- 2, or more common.
...What does all this mean on a practical level? Let's look at some examples to find out. Say you have genital HSV-1 and your partner has genital HSV-2. If you have unprotected sex, there is a small but real risk that you will get HSV-2, resulting in more outbreaks and more shedding. "We have documented cases where a person acquires HSV-2 after a prior genital HSV- 1 infection," says Wald. "I don't think it happens often, but it does happen."
On the other hand, it's very unlikely that your partner will get genital HSV- 1 from you. "I've never seen a case of a person acquiring HSV-1 on top of HSV-2," says Wald. "It's possible, but it would be unusual."
What if your partner has genital HSV-2 and you perform oral sex on him or her? Will you get HSV- 2 in the mouth? Given the widespread practice of oral sex (some three-quarters of all adults practice it, according to The Social Organization of Sexuality, 1994) and the prevalence of genital HSV-2 infection, you might expect oral HSV-2 to be relatively common. It's not.
According to one study, almost 100% of recognizable HSV-2 infection is genital (Nahmias, Scandinavian Journal of Infectious Diseases Supplement, 1990). One reason is that most adults are already infected with HSV-1 orally, which provides some immunity against infection with HSV 2. Another reason is that oral HSV-2 rarely reactivates, so even if an infection does exist, no one knows.
So far we've been talking about transmission of HSV-1 or 2 from its site of preference. What about transmission from another site? Say you acquire genital HSV-1 through oral sex. Can you spread the virus to a partner through genital sex?
The answer is yes, but probably not as easily as it was spread through oral sex. The main reason is that the virus reactivates and sheds less often outside its site of preference. Only about one quarter of people with genital HSV- 1 shed virus at all in the absence of symptoms, while 55% of people with HSV-2 do (Wald, New England Journal of Medicine, 1995). "Shedding data appear to parallel recurrence data, meaning that people who have a lot of recurrences also have a lot of shedding," says Wald.
..."Talk to a wise friend," suggests Rebecca, a health communication specialist on the National Herpes Hotline. "Join a support group. Find Someone you respect and exchange ideas them. It's always reassuring to see that not everyone lives inside the walls our society builds around sexual issues and realities. "...
