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How alike are HSV-1 and HSV-2?
In this feature, we look at the latest scientific facts about the two types of herpes simplex virus, as well as social attitudes toward oral and genital herpes.
When many people first tell someone they have genital herpes, they start by comparing the infection to oral herpes, or cold sores. How apt is the comparison? In spite of scientific facts, the social stigma and emotional attitudes surrounding genital herpes can make it hard to compare it objectively with an oral infection that most people casually accept. Following the unspoken assumptions of our society, many people still believe there is a “good” herpes virus-HSV- 1, the usual cause of cold sores-and a “bad” herpes virus-HSV-2, the usual cause of genital herpes.
In this feature, we take a look at HSV- 1 and 2 to see how alike and different the two viral types really are. We asked leading researchers how the two compare in terms of severity, recurrences, and transmission rates. We asked how often each occurs outside its usual site of preference, and how each behaves in the genital area. We questioned how much immunity having one type orally or genitally provides against getting the second type.
In addition, we looked at the way our society views oral and genital herpes. What’s behind the very different images the two types carry? And what can we do about it? In an interview, counselors at the National Herpes Hotline suggest ways to help replace judgmental social assumptions with a healthy attitude.
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.”
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 which 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. HSV-1 is also the usual cause of herpes whitlow, an infection on the finger, and “wrestler’s herpes,” (herpes gladiatorum) a herpes infection on the chest or face.
The range and potential severity of HSV-1 infections lead some experts to view the virus as more risky than usually perceived. “This is heresy, but I think type 1 is a more significant infection than type 2,” says Spotswood Spruance, MD, an oral HSV specialist at the University of Utah. “Type 1, and the morbidity associated with it, are underestimated.”
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. 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.
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.
How Many Outbreaks?
Just how much of a physical problem HSV poses for a person depends largely on three factors. The first is how well the person’s immune system is able to control the infection.
Differences in immune response may be the main reason that some people are bothered by frequent cold sores or genital herpes outbreaks while others are not. It’s also the reason that both HSV-1 and 2 can pose serious challenges for infants, who have a limited immune response; and for people with compromised immune systems, including people with cancer, AIDS, severe burns, and people taking immunosuppressant medications.
The second factor affecting outbreaks is how long a person has had the infection. Over time, recurrences of both HSV- 1 and 2 tend to decrease, for reasons that aren’t entirely clear.
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, according to Spruance.
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.
According to a study by Wald et al. (New England Journal of Medicine, 1995), among 110 women with genital herpes, the average number of recurrences per year for those with genital HSV-1 was zero. Other studies have shown an average of about one outbreak per year (Benedetti, Annals of Internal Medicine, 1994).
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.
A possible fourth factor affecting recurrence rate is viral type. According to the Lafferty study, genital HSV-2 infections were the most frequently recurring herpes infections, followed by oral HSV-1, genital HSV-1, and last of all, oral HSV-2.
How Easily Spread?
As a number of readers have attested over the years, many people with genital herpes are at least as concerned about transmission-the likelihood of spreading the virus to a partner-as about their own health. On the other hand, few people with oral herpes, share this concern. Is this because one type is more contagious than the other?
The short answer is no. 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.
“Prevalence rates of genital HSV-1 differ based on the practice of oral sex and on the percentage of people who are HSV-1 positive from childhood,” explains Anna Wald, MD researcher at the University of Washington at Seattle.
Finally, the question of immunity and HSV types is complicated by an additional issue. Some studies suggest that the ganglia themselves may acquire some immunity to HSV after they are exposed to one viral type.
In the laboratory, infection of ganglia with more than one virus is difficult, suggesting that it may be more difficult to acquire a second HSV type in a location where you already have HSV. A prior genital infection with HSV-1, for example, may give more protection against genital HSV-2 than a prior oral infection with HSV-1.
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.
While HSV- 1 can be spread from genitals to genitals, “we think it is spread more easily through oral sex because HSV-1 reactivates more frequently in the oral area,” says Wald. However, she warns, “transmission of genital HSV-1 during asymptomatic shedding has been documented.” In other words, genital HSV-1 can be spread through genital sex, even when there are no symptoms. “Good” Virus/ “Bed” Virus
If HSV infection is as easily transmitted from the mouth as from the genitals, then why do people take steps to prevent genital but not oral infection? Why don’t we kiss through dental dams ?
“It’s ironic, isn’t it?” says Wald. “It’s not about health, it’s about social acceptability.”
Scientists can tell us all day that the main difference between the two viral types is simply their site of preference-whether they typically occur above the waist or below. But the unspoken attitudes of our society send a different message. That’s just the problem, social attitudes whisper. Below the waist is bad.
“People think of oral herpes as the “good” herpes and genital herpes as the “bad” kind,” says Glover of the National Herpes Hotline. “It’s partly that they don’t understand the similarities between HSV-1 and 2. But it’s also that good and bad is how our culture views sex and our bodies.”
The inescapable fact is that HSV-1 is usually spread through contact with infected lips, while HSV-2 usually spread through contact with infected genitals. From a social point of view, the problem is not the disease; it’s how you got it.
Whether we like it or not, the social prejudice against genital herpes, no matter which virus causes it, is a reality. “People have more trouble explaining to a new partner that they have genital herpes, even if it’s HSV- 1, than if they have a cold sore,” says Glover. “Just saying the word “genital” is like an anvil that pulls the sentence down”.
Is this topic making you crazy? For people who have trouble dealing with social attitudes toward genital herpes, the blatant double standard society applies to oral herpes can be frustrating, to say the least.
“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. ”
It’s also worth hoping that new research on the similarities between HSV-1 and 2, as well as increased public education about genital herpes, can help lower the level of misunderstanding about both types of the virus. Today, the greatest difference between HSV- 1 and 2 appears to be the way we think about them. Tomorrow, that may change….