Herpes Viral Shedding: The Research and the Rates

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Herpes viral shedding refers to a stage of herpes when the virus becomes active on the skin surface and is contagious. Sometimes, it is asymptomatic viral shedding. Viral shedding with no outward signs helps lead to the silent transmission of herpes to unknowing partners. So how often does viral shedding happen, and how can you be both aware and safe?

Herpes Viral Shedding Asymptomatic

Herpes Viral Shedding Overview

Herpes viral shedding refers to any time the herpes virus becomes active and contagious. The virus hibernates in nerve cells until it decides it’s time to surface to the skin and potentially spread to others through skin-to-skin contact. It’s easy to know herpes shedding is happening when there is a visible outbreak, and thus to avoid sex or contact with the area.

But other times, viral shedding is difficult to pinpoint. When the virus is active and contagious, but there are no symptoms, it’s known as asymptomatic shedding or subclinical shedding. With no outward signs, it’s easy for the virus to spread to unknowing partners — especially when 85% of people with herpes don’t know they have it. Asymptomatic herpes is a major reason the virus is under-diagnosed.

The bottom line is that it’s clear that avoiding sex during visible outbreaks isn’t bulletproof.

Rates of Herpes Viral Shedding

How Long does viral shedding last?

Asymptomatic viral shedding occurs about 20% of the time in people with HSV-2 genital herpes, according to one study. However, the study and others like it uncovered factors that influence this rate. One particular study of women as published in the Annals of Internal Medicine made some interesting findings about shedding frequency.

  • Asymptomatic shedding is higher during the first three months of contracting the virus, suggests the Annals of Internal Medicine study.¹ “Asymptomatic cervical shedding was 3 times more frequent during the first three months after resolution of primary type 2 disease than during later time periods,” it says. ¹
  • Asymptomatic shedding occurs more with genital herpes caused by HSV-2 than genital herpes caused by HSV-1, according to the same study.¹
  • Women previously infected with HSV-1 before acquiring HSV-2 may have a lower rate of asymptomatic genital shedding. “Among patients with type 2 infection, previous type 1 antibody was associated with a lower rate of asymptomatic vulvar shedding.” ¹ (However, another study suggests no difference.²)

Studies that test shedding using the Polymerase Chain Reaction method show a higher rate of shedding than studies that test cultures. For example, the study above was based on PCR testing and showed a 20% rate of herpes shedding. Tests that use cultures, on the other hand, suggest that shedding occurs around 3% of days³. However, PCR is more sensitive and therefore we would assume the results of these studies to be more reliable. Nonetheless, there are some pertinent conclusions to be drawn from studies that use culture testing.

  • The rate of herpes shedding decreases after the first year of infection, according to studies and papers: “Among 227 women with primary genital HSV-2 infection, the rate of shedding from the cervix or vulva decreased from 3.1% of days during the first year, to 2.3% during the second year and 2.1% during the third year.” ³
  • Persons who have HIV as well as herpes experience more frequent viral shedding³.

Another 2011 study used a much larger sample size of 498 HSV-2 infected persons, and also said viral shedding occurs about 20% of days². However, this study included viral shedding that accompanied outbreaks. The study noted that people who tested positive but never experienced herpes symptoms were shedding 10% of the time². The researchers explain that this is because the outbreaks count as times when the virus is shedding. So, according to this paper:

  • There was a 20% rate of shedding if a person has outbreaks.
  • There was a 10% rate if they never have outbreaks.

Not only is there a difference in shedding rates between people with symptomatic and asymptomatic herpes infections, it also matters how many outbreaks you have per year. “Persons with 8 or greater recurrences per year had a viral shedding rate of 18.9% vs 12.7% among persons reporting 1 to 7 recurrences per year,” say the researchers in the study.²

How Long Does Herpes Shedding Last?

A 2008 study published in the Journal of Infectious Diseases measured the duration of “reactivations” of HSV in healthy adults. The sample size included 25 people who tested positive for HSV-2, who were checked via swabs four times a day for 60 days. These were the findings⁴:

  • 24% of the genital herpes reactivations lasted 6 or fewer hours.
  • 49% of the herpes shedding periods lasted 12 or fewer hours.
  • Only 7% were accompanied by visible lesions.

How to Know if You’re Shedding

In addition to abstaining from sex during an outbreak, you probably want to abstain when you are shedding the virus without symptoms. But how do you know if there are no symptoms?

It’s hard to do most of the time, and impossible all of the time. A study in the Journal of Antimicrobial Chemotherapy states that asymptomatic patients can be educated about signs of shedding to be more aware of when the virus has become active, but that these silent recurrences can still go under the radar.³ And currently, there is no herpes shedding test kit to help us out.

Nonetheless, there are things to look out for and be aware of.

  1. Avoid sex for at least a week after any visible outbreaks. A 1995 study in the New England Journal says asymptomatic shedding frequently happens within days of a visible outbreak. “Half the episodes of subclinical shedding of HSV occurred within seven days of a symptomatic recurrence. The risk of subclinical shedding increased with the frequency of symptomatic recurrences.” ⁵ This would suggest that even after your herpes outbreak has cleared up, you are still high risk for transmission for a week afterward.
  2. Be aware of your prodromal symptoms. If you’ve ever had an outbreak, there were probably signs it was coming, such as tingling and discomfort, stress, or fatigue. Be concerned if you have those signs. If you’ve never had an outbreak, be aware of those signs or anything else unusual. For example. there are more unusual symptoms of herpes than the obvious blister. Nerve pain in the leg, for example, happens in some people. Sometimes, asymptomatic carriers of herpes realize they do have symptoms after all once they are educated about them.
  3. Know typical herpes outbreak triggers and avoid them as often as possible. This is standard protocol for people who want to lessen their outbreaks, but perhaps the same logic could be applied to avoiding asymptomatic shedding as well. The most common triggers of herpes activation are stress, a diet with too much arginine, too much UV light, and irritation to the area of infection. Eat a diet for herpes outbreak prevention and practice calm and stress-relief when you can.

Get a 90% Drop in Shedding (And a 1% Transmission Rate)

Reduce HSV-2 Viral Shedding

Couples in which one partner has herpes and the other doesn’t can vastly reduce their likelihood of transmitting the virus. This can be done with suppressive therapy, condom usage, and avoiding sex during high-risk periods like outbreaks.

Antiviral suppressive therapy, meaning taking pills like acyclovir or valocyclovir (Valtrex) on a daily basis, drastically reduces outbreaks and contagiousness from viral shedding. One study found that valocyclovir and acyclovir caused at least a 90% reduction in asymptomatic viral herpes shedding in test subjects.³ (Again, please note that this quote refers to testing of cultures instead of PCR testing, which is why it doesn’t attest to the 20% rate of shedding in the more sensitive studies.)

[quote align=”none” color=”#999999″]”Asymptomatic shedding accounted for nearly half of the total viral shedding noted during the trial. In an intent-to-treat analysis, asymptomatic shedding was detected on 6.9% of days for placebo and on 0.3% of days for acyclovir—a 94% reduction. Reduction of asymptomatic shedding was noted at all anatomical sites. When analysed by PCR, the shedding rates for individual women were reduced by a median of 80% (range, 34–91%). Among specimens that contained HSV DNA, treatment with acyclovir reduced the amount of DNA detected by 90%.”³[/quote]

Coupled with condom usage, which reduces the risk by 30%, or up to 50% in some studies, you can bring the risk down more. A study by the makers of Valtrex suggests that you can manage your risk of transmitting herpes to your partner all the way down to 1% or 2% if you use daily antivirals, condoms, and avoid sex during outbreaks.

The above studies enlighten us that not only should you avoid sex during outbreaks, but also at least one week after the outbreak has cleared, and within the first three months of a first-ever herpes outbreak.

Ongoing research is studying possible future treatments that may be able to be used in conjunction with antivirals to lower the risk even further.


Asymptomatic viral shedding is the clear culprit for herpes being so widespread and yet so under-diagnosed. With the above studies, we learn that people unaware of their status because of having no symptoms are likely to be contagious less of the time. Yet due to this lack of awareness, they transmit the virus more.

And we learn that herpes viral shedding periods lessens over time, although herpes shedding continues to occur.

Luckily, with awareness and precaution, you can manage your transmission risk down so much that it’s downright unlikely you will give your partner herpes.


  1. Koelle, David M., et al. “Asymptomatic reactivation of herpes simplex virus in women after the first episode of genital herpes.” Annals of Internal Medicine 116.6 (1992): 433-437.
  2. Tronstein E, Johnston C, Huang M, et al. Genital Shedding of Herpes Simplex Virus Among Symptomatic and Asymptomatic Persons With HSV-2 Infection. JAMA. 2011;305(14):1441-1449. doi:10.1001/jama.2011.420.
  3. Journal of Antimicrobial Chemotherapy. 2000 Apr;45 Suppl T3:1-8.
  4. Mark, Karen E. et al. “Rapidly Cleared Episodes of Herpes Simplex Virus Reactivation in Immunocompetent Adults.” The Journal of infectious diseases 198.8 (2008): 1141–1149. PMC. Web.
  5. Wald, A., Zeh, J., Selke, S., Ashley, R. & Corey, L. (1995). Virologic characteristics of subclinical and symptomatic genital herpes infections. New England Journal of Medicine 333, 770–5.