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

There are more than half a million new cases of genital herpes in the U.S. every year, according to the CDC. Worldwide, more than 1 in 5 people ages 14 to 49 have genital herpes. 

Most people with genital herpes have no idea they have it. And people can transmit the virus even when they don’t have active symptoms. This means you can get the herpes simplex virus (HSV) even if your partner doesn’t have actual sores on their genitals. So, it’s important to understand how transmission works. This way, you can reduce your chances of getting herpes if your partner is infected. 

How is herpes transmitted?

There are two types of herpes viruses that can cause genital herpes: HSV type 1 and HSV type 2 (HSV-1 and HSV- 2). Each one spreads a little differently. HSV-1 is responsible for most cases of oral herpes, while HSV-2 most commonly causes genital herpes. But this isn’t a hard and fast rule. 

Herpes is generally transmitted through direct contact with the virus or with someone who has the infection. But this can happen in a few different ways. And it is possible to get genital herpes without having sex. 

Genital herpes can be transmitted by: 

• Sexual intercourse with someone who has the virus, even if they have no visible signs

• Any type of direct contact with herpes sores

• Contact with saliva, genital fluids, or mucous membranes (like the mouth or vagina) from someone who has the virus

Many people with herpes don’t know they have it. In fact, estimates show that more than 87% of people with an HSV-2 infection are never diagnosed. 

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

This is a difficult question to answer. The chances of getting herpes from your partner 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

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

What’s the herpes transmission rate among heterosexual couples?

In heterosexual couples, women are more likely than men to get herpes from an infected partner. In other words, a man is more likely to transmit the virus to a woman than vice versa. 

The risk of transmission seems to vary across studies, but most estimates range between 3% and 10%:

• A small study found that men transmitted herpes to women 3 times per 100 unprotected sex acts. 

• Another study found that almost 10% of female partners acquired herpes from an infected male partner within a year. 

• A large study published in The New England Journal of Medicine found that the risk of getting herpes from an infected partner was 3.6% over the course of 8 months. But it’s unclear how many couples in the study used condoms.

What are the chances of getting herpes from a woman?

There isn’t good data on herpes transmission rates from a woman to a man. But we do know that genital herpes is more common in women. About 1 in 5 of women have the virus, compared to about 1 in 10 of men. These rates are even higher among Black individuals.

This tells us that women are more likely than men to carry the virus. But it doesn’t tell us how often she’ll pass the virus to a male partner during sexual intercourse. 

What are the chances of getting herpes with a condom?

Condom use can reduce the risk of herpes transmission: 

• For women, condom use can lower the risk by up to 96%. 

• For men, condoms reduce the risk by about 65%.

While condoms can help reduce the chance of transmission, they don’t completely eliminate the risk. The only guaranteed way to avoid the virus is to abstain from sexual contact. However, another option to further reduce the risk of spreading herpes is a daily antiviral medication. (More on this below.)

What are the chances of getting herpes from oral sex?

Although less common, you can get herpes from oral sex. Both HSV-1 and HSV-2 can cause genital herpes. So, you can get genital herpes if you have oral sex with someone who has oral herpes. The exact transmission rates are unknown. 

People with weakened immune systems can also get herpes in the esophagus (the tube connecting your mouth to your stomach) from contact with HSV in the genital region.

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. Some people also take daily valacyclovir (Valtrex) treatment to reduce asymptomatic shedding and lower the risk of transmission. 

One study looked at how daily Valtrex affected transmission rates of HSV-2. Researchers divided couples into two groups. In one group, the partner with the infection took 500 mg of Valtrex daily. In the other group, the partner took a placebo pill. 

Each group had more than 700 couples. In the Valtrex group, only 14 people (1.9%) got the virus — and only 4 of them developed an outbreak. In the placebo group, 27 people got the infection. This showed that daily Valtrex reduced the chances of passing herpes to a partner.

For people who have nine or fewer herpes outbreaks per year, the dosage of Valtrex is typically 500 mg daily. The dose may be adjusted for those who have more frequent outbreaks, kidney problems, or a weakened immune system. 

Even though herpes is a lifelong infection, many people have fewer outbreaks over time. This means you may be less likely to get herpes from an infected partner over time. But it’s important to know that herpes can still spread even if years pass between outbreaks.

How long does it take for valacyclovir to work?

It’s important to keep in mind that Valtrex isn’t a cure for genital herpes. And the virus can still spread through contagious lesions or shedding even while taking the medication. Daily treatment can reduce the risk of transmission, but it’s not 100% effective.

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

Can you have an outbreak while taking valacyclovir?

Yes. Studies show that daily valacyclovir reduces genital herpes outbreaks by 70% to 80%, but outbreaks can still happen while taking the medication. However, for many people, the frequency of outbreaks tends to go down over time. 

Is Valtrex better than Zovirax or Famvir?

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

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

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Written by:

Nicole Rowe, MD

Dr. Nicole Rowe, MD, is a telehealth family practice physician. She received her medical degree from the University of North Carolina School of Medicine and completed her residency in family medicine at University of Colorado’s Swedish Medical Center.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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