What are the chances of passing herpes during an outbreak

Even Without Sores, Genital Herpes Carriers Infectious 10% of the Time

Table of Contents Show

How Is Genital Herpes Spread?
Genital Herpes Transmission Risk by Gender
Symptomatic vs. Asymptomatic Transmission Risk
Is Undiagnosed Herpes Contagious?
Protection vs. No Protection Transmission Risk
When Should You Get Tested for Genital Herpes?
How to Reduce the Risk of Transmitting Genital Herpes
A Word From Verywell
Frequently Asked Questions

April 12, 2011 -- Even if they don't show any sign of infection, people carrying the genital herpes virus can infect a sex partner 10% of the time.

The finding comes from a large study that collected daily genital swabs from nearly 500 people infected with herpes simplex virus type 2 (HSV-2), the genital herpes virus. Many (18%) thought they were uninfected, but found out they were herpes carriers when they underwent blood tests.

It's not too hard to find people who carry the virus, as 16% of Americans have HSV-2 infections. The vast majority -- between 75% and 90% -- don't know they are infected because they don't get, or don't notice, herpes sores on their genitals.

These asymptomatic herpes carriers shed infectious virus 10% of the 30 or more days they were in the study, report University of Washington researcher Anna Wald, MD, MPH, and colleagues. And nearly all the time, these people had no obvious sign of herpes infection while they were actively shedding virus.

"The primary concern of many HSV-2-seropositive persons is the risk of transmission to sexual partners; in our experience this is the main source of angst in patients with genital herpes," Wald and colleagues note in the April 13 issue of the Journal of the American Medical Association.

Asymptomatic-infected people shed herpes virus only about half as often as do people who have herpes symptoms. But when they are shedding virus, they shed just as much as people who have frequent symptoms (unless they are having an active herpes outbreak).

Wald and colleagues also found that:

Men with genital herpes virus infection shed infectious virus just as often as women do.
Men can shed infectious herpes virus through normal-appearing genital skin.
Infection with HSV-1, the herpes virus that causes cold sores, does not make a person shed HSV-2 more or less often.
It's not clear how much genital herpes virus it takes to infect a person, but evidence suggests only a "relatively moderate shedding episode" can infect a sex partner.
People with eight or more genital herpes outbreaks per year shed infectious virus 31% of the time. People with one to seven outbreaks a year shed infectious virus 19% of the time.
In the Wald study, white people shed virus more often than non-white people, but there were very few non-white people in the study, so the finding is questionable.

Because it's impossible to tell whether a sex partner is actively shedding virus, prevention hinges on knowing whether or not you are infected. You can find out via a simple blood test.

For those who know, or suspect, that they or their sex partner carries the genital herpes virus, each of these steps cuts the risk of transmission in half:

Condom use
Daily use of the herpes drug valacyclovir
Telling your sex partner(s) that you have genital herpes infection

Genital herpes is a sexually transmitted infection (STI) caused by the herpes simplex virus, which comes in two types — HSV-1 or HSV-2. Genital herpes causes outbreaks of genital sores that disappear in days or weeks. Many people who get genital herpes only have mild or no symptoms or only one outbreak. Others could have periodic or even regular outbreaks. Genital herpes is highly contagious, but transmission rates depend on many factors.

This article discusses how genital herpes is spread, the transmission risk, and how to reduce the rate of transmission.

Rowan Jordan / Getty Images

How Is Genital Herpes Spread?

Genital herpes is spread by genital or oral sex with an infected person who might or might not have symptoms. This could include genital contact with:

A genital or oral herpes sore
Fluid from the genitals
Saliva
A finger that has touched the virus
Sharing sex toys with someone who has the virus

Genital Herpes Transmission Risk by Gender

About 12% of people aged 14 to 49 in the United States (around 18 million) have genital herpes. The risk of genital herpes can differ depending on gender and sexual orientation.

The following are relevant findings pertaining to genital herpes transmission risk:

Women are more likely to have genital herpes. This might be because it is easier for the virus to transmit from a man to a woman via penile-vaginal sex.
About 16% of women aged 14 to 49 have genital herpes.
For men aged 14 to 49, the rate of genital herpes is about 8%.
The rate of genital herpes among men who have sex with men is about 16% to 28%, depending on ethnicity. Rates are higher among nonwhite men, and studies say this is likely because of less access to health care and higher poverty rates.
Rates of herpes transmission were lower among gay women (about 2% to 7%) than among bisexual women (about 15% to 17%)

Symptomatic vs. Asymptomatic Transmission Risk

Herpes can be transmitted with or without symptoms. For many people, the first outbreak can be mild or have no symptoms at all. About 88% of people aged 14 to 49 who have herpes have not been diagnosed.

Is Undiagnosed Herpes Contagious?

Yes. Herpes can be transmitted with or without symptoms, and about 88% of people aged 14 to 49 do not know they have herpes. The virus is contagious about 10% of days for people without outbreaks. For those with outbreaks, it is contagious about 20% of days.

Among heterosexual couples who do not regularly use condoms, the transmission rate from a partner who has herpes to one who does not is 5-10% within one year.

Protection vs. No Protection Transmission Risk

A study found that condoms can reduce transmission by 96% from men to women and 65% from women to men. The same study found that among heterosexual couples who do not use condoms, there is a 5 to 10% chance that a person with herpes could transmit the disease to their partner within their first year together.

Experts advise that using condoms during sex (even when there are no herpes outbreaks) and not having sex during outbreaks can greatly reduce the risk of passing on herpes to a partner.

When Should You Get Tested for Genital Herpes?

On average, herpes takes about two to 12 days after sexual contact for herpes symptoms to appear. You should get tested for herpes if:

You're experiencing symptoms like sores, flu-like symptoms, and a foul-smelling discharge from the genitals.
You're pregnant and have had a partner with herpes. Pregnant people with herpes do have a small risk of having herpes simplex virus hepatitis (HSV hepatitis), which is inflammation of the liver. Pregnant people with herpes can also pass on the virus to their babies.
You have multiple sex partners.
You're a man who has sex with men since they are more susceptible to STIs.
You have sex with someone with HIV, increasing the chance of transmitting herpes since a weaker immune system can increase and worsen herpes breakouts.

How to Reduce the Risk of Transmitting Genital Herpes

There are several ways to reduce genital herpes risk, including:

Using a condom correctly and making sure it covers all infected areas during an outbreak
Avoiding sex during an outbreak or if an outbreak seems to be approaching (like if a partner has symptoms such as discharge or itching)
Not sharing sex toys without condoms or without washing them

Summary

Genital herpes is an STI transmitted by the herpes simplex virus via genital contact with an infected person who might or not have visible symptoms of the disease. Herpes can be transmitted via saliva, skin-to-skin contact, shared sex toys, and fingers that have the virus on them. It is recommended to get tested for genital herpes if there are symptoms or if a sexual partner has herpes.

Studies indicate condoms could greatly reduce the chances of transmitting herpes, especially if they cover all areas of an outbreak. Avoiding sharing sex toys and avoiding sex during outbreaks can also minimize the risk of transmitting genital herpes.

A Word From Verywell

Genital herpes transmission can be a worrying subject, especially considering that many people with the disease are not ever diagnosed. Talk to your partner about getting tested and staying safe. Being honest with partners and working with your healthcare provider to stay healthy, especially if you have a weak immune system, is another way to keep you and your partner safer in the future.

Frequently Asked Questions

How easily is genital herpes transmitted?
Herpes can easily be spread from skin-to-skin contact with a person who has the virus. This contact typically occurs during sex when you touch the genitals and/or mouth of the person with the virus.
Is it possible to spread genital herpes without an outbreak?
Yes, about 88% of people with herpes in the United States are not aware they have the disease since many people have no symptoms or mild enough symptoms that they are not tested.
How long does it take for herpes to show up after exposure?
Herpes takes about two to 12 days to show up after exposure. An outbreak can take two weeks to a month to be healed. Taking antiviral medication can reduce the length of an outbreak and prevent future outbreaks.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Centers for Disease Control and Prevention. Genital herpes – CDC detailed fact sheet.
NHS. Genital herpes.
Centers for Disease Control and Prevention. Sexually transmitted infections prevalence, incidence, and cost estimates in the United States.
Okafor N, Rosenberg ES, Luisi N, et al. Disparities in herpes simplex virus type 2 infection between black and white men who have sex with men in Atlanta, GA. Int J STD AIDS. 2015;26(10):740-745. doi:10.1177%2F0956462414552814
Tao G. Sexual orientation and related viral sexually transmitted disease rates among us women aged 15 to 44 years. Am J Public Health. 2008;98(6):1007-1009. doi:10.2105/AJPH.2007.112011
Magaret AS, Mujugira A, Hughes JP, et al. Effect of condom use on per-act hsv-2 transmission risk in hiv-1, hsv-2-discordant couples. Clin Infect Dis. November 17, 2015:civ908. doi:10.1093/cid/civ908
InformedHealth.org. Genital herpes: How can you prevent the spread of herpes in sexual relationships? Institute for Quality and Efficiency in Health Care (IQWiG); 2018.
Centers for Disease Control and Prevention. Genital herpes screening FAQ.
Masadeh M, Shen H, Lee Y, et al. A fatal case of herpes simplex virus hepatitis in a pregnant patient. Intractable Rare Dis Res. 2017;6(2):124-127. doi:10.5582/irdr.2017.01013
MedlinePlus. Herpes (HSV) test.
Planned Parenthood. Oral and genital herpes.

By Neha Kashyap
Neha is a New York-based health journalist who has written for WebMD, ADDitude, HuffPost Life, and dailyRx News. Neha enjoys writing about mental health, elder care, innovative health care technologies, paying for health care, and simple measures that we all can take to work toward better health.

Thanks for your feedback!