STD Awareness: Asymptomatic Shedding of Herpes

Q: Can I catch herpes if my partner isn’t having an outbreak?
A: Yes, your partner can transmit the virus even if he or she isn’t experiencing symptoms. In fact, most genital herpes infections are transmitted in the absence of symptoms.

When most people think about genital herpes, they think about the symptoms that are associated with it: clusters of blistery sores around the genitals or buttocks. But most genital herpes infections don’t have symptoms — they are asymptomatic — or the symptoms are so mild or nonspecific that the person suffering from them doesn’t even make the mental connection. It is estimated that only 10 to 15 percent of people with herpes exhibit symptoms, which may be a silver lining for the millions who unknowingly carry the virus, but it also helps it spread more easily.

What is genital herpes, anyway?

Genital herpes can be caused by two types of herpes simplex viruses — either herpes simplex virus type 1 (HSV-1) or herpes simplex virus type 2 (HSV-2). The difference between the two viruses is that HSV-1 is more active when it infects the facial region, where it can cause cold sores; HSV-2 is more active when it infects the genitals. Genital infections with HSV-1 tend to be milder than genital infections with HSV-2. The Centers for Disease Control and Prevention states that, among Americans 14 to 49 years old, 1 out of 5 women and 1 out of 9 men have a genital HSV-2 infection. Because that stat doesn’t count genital HSV-1 infections, the overall number of people with genital herpes is actually higher.

An “outbreak” occurs when genital herpes symptoms appear. The most well-known symptom is a cluster of blisters or open sores in the genital or rectal area. Other symptoms, which might be mild or might not be recognized as being part of an infection, include:

  • very small lesions
  • itching
  • soreness
  • genital pain
  • tingling or shooting pains below the waist
  • during the first outbreak: flu-like feeling, fever, chills, or swollen glands

These symptoms are very common, and we could experience any of them on any day for a number of reasons, so it’s quite possible for someone to experience them as a result of a genital herpes infection but not make the connection. Some people with herpes infections learn to recognize these subtle cues to better predict when the virus is flaring up, which could help them avoid transmitting the virus to their partners.

How is herpes spread without an outbreak?

People infected with HSV periodically go through phases in which they are “shedding” the virus, meaning that their bodies are producing infectious virus particles that can be transmitted to others through close contact. HSV can originate from a number of places, including the vulva, cervix, penile skin, scrotal area, urethra, anal area, feces, urine, and semen.

When someone infected with HSV experiences genital blisters or sores, he or she is certainly shedding virus as well. But the virus can also replicate silently, meaning that you don’t experience symptoms but you do produce copies of the virus, which you can potentially transmit. It’s much more common to shed virus when no genital lesions are present — this phenomenon is called asymptomatic shedding.

About 75 percent of asymptomatic shedding events only last for a day, while viral shedding lasts longer when accompanied by symptoms. Asymptomatic shedding is partially influenced by a few factors:

  • HSV type: A genital HSV-1 infection is milder than a genital HSV-2 infection. Genital HSV-1 infections have fewer recurrences and are associated with less asymptomatic shedding.
  • Duration of infection: While it’s thought that viral shedding never ceases completely, the rate does seem to decrease over time. Someone who has been infected with HSV for many years probably sheds less virus than someone who has recently acquired the infection.
  • Immune status: A compromised immune system might increase the rate at which someone with an HSV infection sheds virus. For example, people with HIV might shed HSV at a higher rate than their HIV-negative counterparts.

Older studies on asymptomatic shedding relied on a technique called “viral culture” to detect HSV from subjects, and found that people with herpes infections were asymptomatically shedding on around 1 to 4 percent of days. Recently, however, researchers started using PCR, a highly sensitive technology that can “amplify” DNA from very small sample sizes — and they are finding higher rates of asymptomatic shedding. For instance, one team found that females with recent HSV-2 genital infections shed virus on 28 percent of days on average. Males with recent HSV-2 genital infections, or a history of frequent herpes outbreaks, were found to shed virus on 32 percent of days on average. Other studies have had similar findings.

The rate of asymptomatic shedding varies from individual to individual. Thanks to genetic variation, our immune systems are all different, and there are even slight genetic differences between HSV strains, leading to unique host/virus interactions. Unless we are being studied by herpes researchers, we can’t know for sure how often we are asymptomatically shedding.

If I have genital herpes, how can I protect my partner?

Most HSV transmissions occur during periods of asymptomatic shedding, but there are still preventive steps you can take. If you have a genital HSV infection, you can:

  • use condoms consistently and correctly, if you or your partner has a penis
  • use dental dams for cunnilingus or anilingus if the giving partner has an oral HSV infection, or if the receiving partner has a genital HSV infection
  • consider herpes medications, such as acyclovir or valacyclovir, which decrease rates of asymptomatic shedding (and outbreaks!)
  • seek education from a sexual health provider, who can help you recognize mild or atypical herpes outbreaks
  • in the event of symptoms, practice abstinence until seven days after genital lesions have healed

Need more information? Make an appointment at a Planned Parenthood health center to be tested for HSV or to learn about safer sex, herpes medication, and more. And drop by any time to pick up latex condoms, female condoms, and dental dams!

Click here to check out other installments of our monthly STD Awareness series!

13 thoughts on “STD Awareness: Asymptomatic Shedding of Herpes

  1. Pingback: STD Awareness: How Can I Protect Myself if My Partner Has Herpes? | Planned Parenthood Advocates of Arizona | Blog

  2. Hi Anna, there is a raft of new medical research that strongly suggests anti-viral medications (acyclovir) have no impact on shedding and only reduce frequency of outbreaks. Given this, it may be prudent to amend the third bullet point in your summary above.

    • If anti-herpes meds are shown to reduce transmission, then it would seem they do have an impact on shedding (volume, frequency, or both). Can you please provide links to this raft of new research? If you read the Commenting Policy (don’t worry, I doubt anyone has), you’ll see that commenters are strongly encouraged to include links when making factual claims. Thanks!

      • Hi Anna, thanks for responding. There are many articles on this; one is titled: “Herpes Drugs Don’t Stop Herpes Shedding”

        The key insight is that “while drugs like acyclovir (Zovirax) “ameliorate” clinical disease, they do not reduce viral shedding and only partly block sexual transmission.

        However, a new drug, Pritelivir supposedly Blocks Viral Shedding.

        Pritelivir and acyclovir may work well together, although trials are underway to understand if there are any adverse reactions. At x70 dose in primates, there were some fatalities. Eeek.

        Hope this helps.

        • Oh, I see what you’re saying. The WebMD article says that herpes medications don’t STOP shedding. But the claim made here is that they REDUCE shedding. So, while it would be great to develop a drug that actually stopped viral shedding completely, a drug that reduces shedding is nothing to sneeze at.

          It’s important for people to understand that these drugs reduce, but do not eliminate, risk, just as do other preventive measures like abstinence during outbreaks and the use of condoms. But using all preventive strategies simultaneously can be the best way to reduce risk of transmission between discordant partners.

          Here is the original study that the WebMD article was based on:
          I have downloaded the PDF to read in more depth later, but the results of the study showed that the drugs did significantly reduce viral shedding. Last I checked, we don’t know what the infectious dose of herpes simplex virus is (so we don’t know to what level viral shedding must be reduced in order to render someone effectively noninfectious), but the fact that these drugs reduce transmission is a clue that shedding is often — but not always — sufficiently reduced to be protective.

  3. Hi Anna,

    I’m concerned about your certainty of facial HSV- 1 conferring no or very little immunity to subsequent genital re-infection. I have read many other posts suggest otherwise. Can you, please, clarify on the possibility or at least ease of contacting gential HSV- 1 in the face of past occurrence of facial cold sores (confirmed to be HSV- 1)?

    Please see various sources suggesting contrary to your position:

    Prevention and Transmission:

    Antibodies that develop following an initial infection with a type of HSV prevents reinfection with the same virus type—a person with a history of orofacial infection caused by HSV-1 cannot contract herpes whitlow or a genital infection caused by HSV-1. In a monogamous couple, a seronegative female runs a greater than 30% per year risk of contracting an HSV-1 infection from a seropositive male partner.

    Type specific HSV tests often use a technology called enzyme linked immunosorbent assay, or ELISA (or sometimes just called enzyme immunoassay, or EIA). The outcomes often are expressed as an ELISA (or EIA) ratio, i.e. the strength of the reaction in the patient’s specimen divided by the strength in a negative control specimen. In other words, it is not measuring an actual antibody level, just the strength of a chemical reaction. For the most commonly used type specific HSV-1 and HSV-2 ELISA tests, ratios below 0.9 are negative, 0.9 – 1.1 are officially considered equivocal.

    You don’t say what your partner’s HSV-1 test result showed. If it is positive, there is no chance she will acquire your presumed HSV-1 infection; she would be highly resistant to catching a new HSV-1 infection, anywhere on her body. If her HSV-1 test is negative, then there is at least a theoretical chance you could infect her by kissing her or performing oral sex on her. But even in that situation, most partner of infected people never catch it themselves.

    The interpretation of HSV blood tests has been discussed in great detail, and many many times, on this forum. Use the search link if you need more information.

    Others exist.

    • Hi Max. When writing my posts about herpes, I stuck with a medical textbook (this behemoth to be exact) and many articles from medical journals. I don’t think I ever said that “facial HSV-1 confer[s] no or very little immunity to subsequent genital re-infection.”

      I have said that if you have an oral HSV-1 infection, you might have some degree of protection against acquiring HSV-1 infection in your genitals — but we don’t know to what degree a previous HSV-1 infection protects us from subsequent infections elsewhere in our bodies. More study is needed to answer this question more fully, but the short answer is that yes, reinfection in the genitals is possible.

      Perhaps in the near future I will go more in depth into this topic, as it is a source of conflicting information on the Internet.

    • Does this same logic apply to HSV2? If someone is infected on the genitals with HSV2 and was not infected in the mouth during the initial infection. Is it true that their body will product antibodies so they can’t contract oral HSV2?

      I ask because I know someone whose husband contracted genital HSV2 from her. She definitely performed oral sex on him over 10 years or so (they are now divorced). I do not have HSV2 nor desire the risk to receive it even orally. I know it is very low risk anyhow. She never had any of this knowledge so I would like to help her. Please advise.

      • The body does not produce very good natural immunity to HSV infections (which is perhaps one reason why we still don’t have a herpes vaccine). Infection with HSV-1 or HSV-2 in one part of the body does not mean that one is immune to being infected with the virus in another part of the body, though their risk could be lower and symptoms, if they appear, could be milder. There is some further information in this post.

  4. Hi, I’m confused at the amount of information on the internet, I need it broken down into a simple form.
    I have had hsv2 since 2013,first outbreak was severe and was hospitalised on drip. I am female.
    I do not get any outbreaks I haven’t had one since 2013.
    If I was to take avycloir and use condoms what risk am I of spreading this virus. In a simple form how possible is it?
    I don’t have a clue if I am ever shedding. Is viral shedding when there is a outbreak and is asmosynic shedding just daily in life with no outbreak. I’m not understanding the difference.

    • One study that looked at condom use found that for every 10,000 acts of vaginal or anal intercourse, 8.9 women acquired HSV-2 from their male partners, while 1.5 men acquired HSV-2 from their female partners. Additionally, someone with genital herpes can consider daily herpes medications, such as acyclovir, which has been found to reduce viral shedding by as much as 94 percent. Check out this article for more information.

  5. Hi,
    If you have hsv1 oral herpes what can you take to reduce the chances of giving it to your partner and by what percentage is the risk reduced? Also what are the chance you will give it to your partner from kissing anyways? I can’t seem to find any statistics on this. It seems like a lot of the info on the web is about hsv2 genital herpes.

  6. I’d like to know how anyone was able to determine that a medicine reduced shedding by 94%. If they were able to determine that shedding was reduced, that implies they were able to know WHEN the shedding occurred before the person started on meds as well as after. So the question is HOW did they do this? Did they use a type of pH paper, testing swan or dipstick? If they could quantify it, then those with HSV should be able to have access to such testing materials so they know when they are shedding. That is a very viable market right now while they figure out a cure or vaccine.

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