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HomeHealth ConditionsHerpes

What Are the Chances of Getting Herpes From an Infected Partner?

Nicole Rowe, MDKatie E. Golden, MD
Written by Nicole Rowe, MD | Reviewed by Katie E. Golden, MD
Updated on February 23, 2024

Key takeaways:

  • Genital herpes is a very common infection. And you can get herpes from a partner who has the infection even when they have no active symptoms or sores.

  • Herpes transmission rates vary based on a lot of factors. In heterosexual couples, women are more likely to get infected from a man. Transmission rates from a woman to a man are lower.  

  • It’s best to avoid sexual intercourse while your partner has a herpes outbreak. And when your partner is infected but doesn’t have symptoms, you can lower your risk of herpes transmission with medication and condoms.

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There are more than half a million new cases of genital herpes every year, according to the CDC. And more than 1 in 10 people in the U.S. ages 14 to 49 years has the virus that causes genital herpes. 

Most people are surprised to hear that they can transmit the herpes simplex virus (HSV) even when they don’t have active symptoms. This is called “asymptomatic shedding.” And it means you can get HSV even if your partner doesn’t have actual sores on their genitals. Despite these risks, you can take action to prevent transmission.

Here are the main things to know about reducing the risk of transmitting genital herpes from someone with an infection to someone who doesn’t have one.

How is herpes transmitted? 

The herpes simplex virus 2 (HSV-2) is the virus that most commonly causes genital herpes. It can spread through direct contact with herpes sores. But it can also spread even when no visible signs are present — through contact with skin or mucous membranes (like the mouth or vagina). And many people with the infection may not know they have herpes. In fact, estimates show that more than 87% of people with an HSV-2 infection never get diagnosed. 

What are the chances of getting herpes from an infected partner?

This is a difficult question to answer. It depends on these factors: 

  • The type of sex you have

  • Whether active genital lesions are present

  • Condom use

  • The frequency of sex acts

  • Whether the susceptible partner has a weakened immune system

  • Whether the partner with the infection is taking antiviral therapy  

Most research on HSV transmission comes from studies on heterosexual couples, so we’ll go through some of the details next. More research is needed to know how transmission rates change or vary in same-sex or transgender couples.

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What’s the herpes transmission rate among heterosexual couples?

In heterosexual couples, men are less likely than women to get herpes from a partner with the infection. In other words, it’s more likely that a man will transmit the virus to a woman, rather than a woman to a man. 

The likelihood of transmission seems to vary among studies, but many of the reports range between 3% and 10%. In one small study, the rate at which men transmitted herpes to women was 2.9 times per 100 unprotected sex acts. 

But, in a different study, almost 10% of female partners acquired herpes from a male partner over the course of a year. In yet another large study, published in The New England Journal of Medicine, the risk of getting herpes from a partner with the infection was 3.6% over the course of 8 months. It’s unclear how many couples in this study used condoms.

What are the chances of getting herpes from a woman?

There’s no good data on the herpes transmission rates from a woman to a man. But the CDC does report numbers on how common it is by sex. About 16% of women have the genital herpes virus, but only about 8% of men have it. And these rates are higher if you look specifically at Blacks.  

This tells us that a woman is more likely than a man to carry the virus. But it doesn’t tell us the chances she will pass the virus to a male partner during sexual intercourse. 

What are the chances of getting herpes with a condom?

Condom use can lower that risk for women up to 96%. It’s somewhat less helpful in protecting susceptible men, with a 65% reduced risk.

Other than abstaining from sexual contact, there’s no proven way to completely prevent getting the virus from your partner. While condoms can help reduce the chance of transmission, they don’t completely eliminate the risk. However, another option to further reduce the risk of spread is daily antiviral medication (more on this next).

What are the chances of getting herpes from a partner on HSV medication (valacyclovir)?

While there’s no cure for HSV-2, there are medications that can decrease the length and severity of outbreaks. And some people take daily valacyclovir (Valtrex) treatment to reduce asymptomatic shedding and the likelihood of transmission. 

In the study published at The New England Journal of Medicine, they also looked at how daily Valtrex affected transmission rates. Researchers divided the couples into two groups. In one group, the partner with the infection took daily Valtrex. In the other group, they took a placebo pill. 

Each group had more than 700 couples. In the group that took daily Valtrex, only 14 people (1.9%) got the virus — and only 4 of them developed an outbreak. In the group that took placebo, 27 people got the infection. This showed that taking 500 mg of Valtrex daily reduced the transmission of genital HSV-2 to the partner without the infection.

Although HSV-2 causes most recurrent genital herpes, an increasing number are caused by HSV-1 transmitted during oral sex. HSV-1 is the herpes simplex virus most commonly associated with cold sores on and around the mouth. Valtrex can be helpful to reduce transmission of HSV-2. But researchers haven’t studied it in people with genital lesions due to HSV-1. 

For people who have nine or fewer recurrences of an HSV-2 outbreak per year, the dosage of Valtrex is typically 500 mg daily. For those who have more frequent outbreaks, kidney problems, or a weakened immune system, dosing may be adjusted. 

How long does it take for valacyclovir to work?

It’s important to keep in mind that valacyclovir (Valtrex) isn’t a cure for genital herpes. And contagious lesions or shedding may still occur while taking the medication. Daily treatment can reduce the risk of transmission, but it isn’t 100% guaranteed that you won’t get the infection.

If your partner has an active outbreak (lesions and/or other symptoms), it’s best to avoid sexual contact even if they’re taking the medication. It’s impossible to know if and when asymptomatic shedding is happening, so experts advise consistent condom use as an additional precaution.  

Can you have an outbreak while taking valacyclovir?

Yes. Studies show that daily valacyclovir reduces genital herpes outbreaks by 70% to 80%, but it’s still possible to have an outbreak while taking the medication. However, the frequency of outbreaks tends to go down over time for a lot of people. 

Is Valtrex better than Zovirax or Famvir?

Valacyclovir isn’t the only medication approved to treat genital herpes. To treat herpes outbreaks, valacyclovir (Valtrex), acyclovir (Zovirax), and famciclovir (Famvir) appear to be equally effective. Zovirax is approved to treat only initial and recurrent outbreaks. 

Compared with Famvir, Valtrex appears to be more effective at suppressing viral shedding when taken daily. Of the three medications, Valtrex is the only one approved for reducing the transmission of genital herpes.

Can you get herpes from oral sex?

Although it’s less common, you can get herpes from oral sex. Any contact with mucus membranes or skin with an infected partner has the potential to transmit herpes. Both HSV-1 (which causes cold sores) and HSV-2 can cause genital herpes. People with weakened immune systems can get herpes in the esophagus (the tube connecting the mouth to the stomach) from contact with HSV in the genital region.

The bottom line

Genital herpes (HSV) can be transmitted even when a person with the virus doesn’t have genital sores. Many people who carry HSV don’t even know they have the infection. Herpes is very contagious and common, so it’s important to use condoms consistently and correctly. This can help reduce transmission if one partner has herpes. 

If a partner knows they’ve had HSV, taking a daily antiviral medication can reduce the chances of passing it along to partners. But neither condoms nor antiviral medications can completely eliminate the risk of transmitting herpes to other people. 

References

Bryant Ranch Prepack. (2020). Valacyclovir hydrochloride [package insert].

Centers for Disease Control and Prevention. (2021). Genital herpes: CDC detailed fact sheet.

View All References (6)
GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

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