Can you transmit herpes without having symptoms

According to a new study, people who test positive for herpes simplex virus-2 can shed the virus even though they have no symptoms. Infectious disease expert Dr. Peter Leone discusses how herpes is spread and whether people without symptoms should be tested for the virus.

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IRA FLATOW, host:

You're listening to SCIENCE FRIDAY. I'm Ira Flatow.

Up next, well, we're going to talk about something that was kind of surprising, some research reported in the Journal of the American Medical Association this week, and it showed that herpes simplex virus type 2 - that's the virus usually associated with genital herpes - that virus can be spread by a person who has no symptoms of the infection. Those spreading the virus may not know they are even infected because they've never been diagnosed or tested or show any symptoms sometimes.

My next guest says most of the people who are infected with herpes type 2 don't even know they're infected, and in that light doctors should be routinely testing for herpes using a blood test.

Joining me now to talk about it is Peter Leone. He's professor of medicine in the School of Medicine, University of North Carolina, adjunct professor of epidemiology, Gillings School of Global Public Health, medical director of the North Carolina HIV/STD Prevention and Control Branch.

Welcome to SCIENCE FRIDAY.

Dr. PETER LEONE (University of North Carolina): Well, thank you, Ira. It's good to be with you.

FLATOW: Let's talk a bit about the two types of herpes virus for a second here. Can you describe the difference?

Dr. LEONE: Oh, sure. So there are a bunch of different human herpes viruses. The two we're going to be talking about is herpes simplex 1 and 2. And they are very similar. About 85 percent of the genetic material, these viruses are the same, but evolutionarily they sort of diverged years ago when humans started having sex face to face.

So what we see are, generally speaking, viruses that are similar, can cause lifelong infection in the case of both herpes simplex 1 and 2, but the natural history is different for both of them.

The idea, though, that HSV-2 is exclusively below the waist, and HSV-1 is exclusively above the waist causing cold sores is no longer true. So we really need to educate folks about what the differences are and why it's important to make the diagnosis to begin with.

FLATOW: And this new research that was published this week showing that a lot of people could have genital herpes and do have it and have no idea they have, have it, because they don't have the symptoms...

Dr. LEONE: Exactly. I mean, what's striking is that we've known this for quite a while and yet we haven't been able to get any traction - we being folks in public health - to get both clinicians and the general public to understand that this is a widely prevalent infection, and that indeed most of the folks do not recognize that they're infected.

So if you look at the numbers, about 17 percent of adults - and that's individuals between the ages of 14 and 49 years of age - have genital herpes due to HSV-2 in the United States.

Eighty-five percent of those folks don't know they're infected.

FLATOW: Wow.

Dr. LEONE: Yeah. I agree.

(Soundbite of laughter)

FLATOW: And they - so - and knowing - you would know you're infected in what way?

Dr. LEONE: Well, that's the problem. The classic description of genital herpes doesn't really match what we know in terms of the natural history normally. What I mean by that is if you pick up a textbook, you'll hear about all these painful ulcers and lesions, and you know, they last for days. The truth is that a minority of folks present that way.

Most folks, if they have symptoms, the symptoms are pretty mild - burning or itching that may last for a couple of days and goes away. So what we see are folks who either get misdiagnosed or they treat themselves, and of course it goes away so they think they don't have anything to worry about. And that's only part of the problem.

So if you're having symptoms, you may, you know, proceed to go in and see someone, but there's so much stigma associated with the diagnosis that most folks aren't willing to go in and actually even have a discussion about something that might be occurring on their genitals with their physician or anybody else for that matter.

FLATOW: So it's a sort of don't ask, don't tell?

Dr. LEONE: Yeah. But in this case there are some real consequences because don't ask, don't tell means your life goes on but the virus goes on with you, and as a result you can transmit it to other folks.

FLATOW: And what about using safe sex with condoms? Does that prevent the transmission?

Dr. LEONE: Well, I like to use the term safer sex because I don't think that sex is ever entirely safe for lots of reasons, but condoms reduce the risk of transmission by about 50 percent. Depending on the studies, it looks like it's 25 to 50 percent. It's not a hundred percent. But that requires that you use them, use them consistently, and recognize that just because you think you don't have herpes, or you may ask your partner if they have it, doesn't mean that either one of you don't have the infection.

So there's lot of reasons to use condoms, primarily in the United States around HIV transmission, but we also know that condoms help to reduce the risk of transmission of herpes.

FLATOW: So are you suggesting then that this should be part of a routine screening maybe with your health checkup?

Dr. LEONE: I am. I think ELISA should be made available to folks who want to know. And only to backtrack for a second - we talked about 17 percent of adults being infected in the United States, but this idea is sort of like, well, it's for other folks who get it. And there isn't great correlation in terms of the number of sexual partners and what your risk is, in addition because this is a lifelong infection. As the population ages up, the overall percentage of folks infected increases as well because there's no cure.

So if you look at some population-based data in the United States and look at unmarried adults, meaning folks between the ages of 45 and 50, for women, we know the prevalence rate for genital herpes due to HSV-2 is between 50 and 70 percent. So we're looking at close to the majority or the majority of folks in that age group who are single having genital herpes. So...

FLATOW: Let me go over that number again because you're saying that - it's hard to believe - you're saying that for women between the age of 40 and 50...

Dr. LEONE: Right.

FLATOW: ... unmarried women?

Dr. LEONE: Yes, unmarried women.

FLATOW: You're saying that between 50 and 75 percent of them have herpes type 2?

Dr. LEONE: That's exactly right. Yeah.

FLATOW: Wow.

Dr. LEONE: I know. It causes me to pause. I read the article about five times myself, saying, wow, and I do this for a living.

My point is that we're sort of taken back by it. But the one simple thing we can do to actually sort of raise awareness is going in and getting a blood test. And the problem we get into is most people feel, well, if I'm not having symptoms, I don't have to worry about it.

In the article that you cited, the JAMA article from Anna Wald and colleagues out of the University of Washington, shows that almost everyone who's infected will shed the virus asymptomatically, meaning there's no signs or symptoms. And yet, if you were to actually take a swab around the genital track area, you could find HSV-2 present.

FLATOW: Mm-hmm.

Dr. LEONE: Significant number of days in almost all of those folks. For folks with any reported symptoms, meaning they've had at least one outbreak or more a year, it's about 20 percent of days. But for folks with absolutely no reported symptoms of genital herpes, and that's after educating them to recognize signs and symptoms, it was 10 percent of days that you could actually find virus present in the genital track. And that's by once a day swabbing. So we actually think that the shedding rate may be higher than that.

FLATOW: Mm-hmm. And can you spread genital herpes by having oral sex?

Dr. LEONE: Yes. And so what we're seeing is oral transmission that's primarily due to transmitting HSV-1 from mouth to genitals. So about 50 percent of the new genital herpes infections that we're seeing in the young adults now are due to HSV-1. And the clinical presentation for that is identical to HSV-2.

So by just sort of doing an examination, you can't distinguish type 1 from type 2. But the natural history is different from these two infections. So for HSV-2, the reason why we're concerned about is obviously transmission to partners. But there is a strong association of increasing the risk of HIV acquisition and transmission with HSV-2.

FLATOW: Mm-hmm. Because the immune system is compromised?

Dr. LEONE: Well, you've got a breach in the skin, so the barrier that's there with normal skin, the genital track in the vagina on the penis, can be disrupted with ulcers. But we also know that chronic shedding of virus causes local inflammation. By inflammation, I don't mean that you've got redness or tenderness on the mucosal surface. But you have immune cells that are pulled up near the skin at the end of the sensory neuron and actually is there removing virus. Those same cells though can be docking points for HIV.

So the increase risk is about two to three-fold greater for folks with HSV-2, compared for those folks who do not have genital HSV-2 infection. So it's a significant driver of the HIV epidemic in the United States for both men who have sex with men and for heterosexual individuals.

FLATOW: Sue(ph) in Hastings, Michigan. Hi. Welcome to SCIENCE FRIDAY.

SUE (Caller): Hi.

FLATOW: Hi, there. Go ahead.

SUE: I'm sorry?

FLATOW: Go ahead.

SUE: I have a question. I know of several people who give blood regularly. And I know of people - I have people and acquaintances and relatives of mine who also received blood. Now, is this something that the Red Cross and like the hospitals that do blood-taking, or blood-receiving maybe is better way of putting it - anyway, do they test for herpes?

Dr. LEONE: No, they do not.

SUE: (Unintelligible) you give someone herpes through the blood or is it somehow identically fixed?

Dr. LEONE: Well, so herpes is a skin to skin transmission infection, meaning you've got to come in contact with the virus in someone's skin and actually get it inoculated into your skin. So it's intimate contact. And in terms of HSV-2, we're talking about sexual contact. But that doesn't mean that you have to have penetrative sex because you can shed virus from any area of the genital track. So intimate contact, skin-to-skin contact results in transmission if the virus is present.

FLATOW: And so it can can it be passed through a blood transfusion?

Dr. LEONE: No.

FLATOW: No. OK.

Dr. LEONE: No. And they don't routinely screen for HSV-1 or 2 in the blood supply.

FLATOW: And why is it not now generally given in your doctor's office as a screening?

Dr. LEONE: Because the information that we just shared is either underappreciated or not known at all among clinicians. So there's viewed this sort of thing, like, well, it's not something I have time for. I don't want to deal with counseling. And it's viewed as a nuisance disease without under any understanding that we see consequences: neonatal herpes, meaning transmission from mother to infant or the role that herpes plays in HIV.

That aside, I can tell you, making the diagnosis in someone who comes in with an outbreak, it's devastating for them. And it's a lifelong issue because of the concern of transmission to new partners.

FLATOW: And so your recommendation, then, is to have screening done routinely in doctor's office?

Dr. LEONE: I think any sexually active adult who wants to know their status should be offered that.

FLATOW: Can you ask for it if you're not offered it?

Dr. LEONE: Yes, you can. And there are reliable blood tests now that distinguish between HSV-1 and HSV-2. So we would ask that someone goes in and requests a type-specific test for HSV. And that will be an antibody test for HSV-2 that can tell you whether or not you have antibodies. And the other nuance here that needs to be picked up is that if you have antibodies to HSV-2, you're infected. If you're infected, you have genital infection. And if you have genital infection with HSV-2, you will shed the virus.

FLATOW: Mm-hmm. And as you say right from the beginning, most cases, you don't even know it.

Dr. LEONE: No. 85 percent of people are unaware.

FLATOW: Oh. What about antiviral medications? Are they effective?

Dr. LEONE: Well, they work. So we've got three approved antiviral medications: aciclovir, famciclovir, valaciclovir. Two of those are now available generically. And they work to control outbreaks, and they work to reduce the risk of transmission. But in order to reduce transmission, you have to take those drugs daily. But that also means that you need to know that you're infected to take it.

FLATOW: And that's where we started the whole discussion.

Dr. LEONE: Exactly.

FLATOW: Not knowing that you're infected. Well, thank you. This is very informative, Dr. Leone.

Dr. LEONE: Well, I appreciate you taking the time out for this.

FLATOW: Thank you very much.

Dr. LEONE: All right. Take care.

FLATOW: You're welcome. Peter Leone is a professor of medicine in the School of Medicine at University of North Carolina and adjunct professor of epidemiology at the Gillings School of Global Public Health and the medical director of the North Carolina HIV/STD Prevention and Control branch.

I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.

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