Herpes can be a sexually transmitted disease, but it isn’t always one. The answer depends on which type of herpes simplex virus is involved and how it was transmitted. Genital herpes, caused by either HSV-1 or HSV-2, is classified as an STI by the CDC. But oral herpes, the kind that causes cold sores, is most commonly picked up during childhood through non-sexual contact with saliva.
Two Types, Two Different Stories
There are two types of herpes simplex virus. HSV-1 primarily causes oral herpes, producing cold sores or fever blisters on or around the mouth. HSV-2 primarily causes genital herpes and spreads through sexual contact. Both types spread through skin-to-skin contact, but the routes they take are quite different.
Most people with HSV-1 pick it up during childhood or young adulthood from non-sexual contact, such as a kiss from a relative or sharing a drink. In that context, it’s not an STD at all. However, HSV-1 can spread from the mouth to the genitals during oral sex, causing genital herpes. When that happens, it is sexually transmitted. An estimated 376 million people worldwide have genital HSV-1 infections, making this crossover far from rare.
HSV-2 is a different picture. It spreads almost exclusively through sexual activity, via contact with genital or anal surfaces, skin, sores, or fluids of an infected person. About 520 million people aged 15 to 49 had genital HSV-2 in 2020. HSV-2 is, by any definition, a sexually transmitted infection. It’s also possible to carry both types at the same time, which roughly 50 million people do.
How Common Herpes Actually Is
More than 1 in 5 adults worldwide between 15 and 49 are living with a genital herpes infection. That’s around 846 million people. When you add oral HSV-1 infections, which affect the majority of the global population, herpes is one of the most widespread viral infections on the planet. Most people with oral herpes have no symptoms at all, which is one reason it spreads so easily and why many people don’t realize they carry the virus.
Transmission Without Symptoms
One of the trickiest aspects of herpes is that it can spread even when no sores are visible. This is called asymptomatic shedding, where the virus is active on the skin’s surface without causing noticeable blisters. In the first few months after a genital HSV-1 infection, viral shedding occurs on roughly 11% of days. By a year after infection, that drops to about 5% of days. HSV-2 follows a similar pattern.
This means someone can transmit herpes to a partner without knowing they’re infectious. It’s a major reason herpes is so widespread and why many people are genuinely surprised by a positive test result.
How Herpes Spreads (and How to Reduce Risk)
Genital herpes spreads through vaginal, anal, or oral sex with someone who carries the virus. Direct skin-to-skin contact is the primary route. You don’t need to have intercourse to transmit it; contact with an area where the virus is shedding is enough.
Condoms reduce the risk significantly, though they don’t eliminate it because herpes can affect skin that a condom doesn’t cover. Research on couples where one partner had HSV-2 found condoms were 96% effective at preventing transmission from men to women and 65% effective from women to men. The difference comes down to anatomy: condoms cover more of the skin surface that transmits the virus in one direction than the other.
Daily antiviral medication taken by the infected partner cuts the transmission rate roughly in half. In one study, 1.9% of partners became infected over eight months when the source partner took daily antivirals, compared to 3.6% with a placebo. Combining condom use with daily antivirals brings the risk down further.
Testing and Diagnosis
If you have visible sores, a healthcare provider can test them directly with a swab. For people without symptoms, blood tests can detect antibodies to HSV-1 and HSV-2 separately. These antibodies develop in the first weeks after infection and stick around permanently.
Timing matters for blood tests. If you think you were recently exposed, antibodies may not show up right away. The CDC recommends retesting 12 weeks after a suspected exposure to get an accurate result. Testing before that window closes can produce a false negative.
Routine herpes screening is not recommended for everyone. Testing is typically offered to people presenting for an STI evaluation, those with multiple sexual partners, people with HIV, and pregnant women. The reason screening isn’t universal is partly because a positive result in someone without symptoms can cause significant distress without necessarily changing their medical care.
Why It Matters During Pregnancy
Herpes poses a serious risk to newborns, particularly when a mother acquires a primary (first-time) infection during the third trimester. Transmission rates to the baby during delivery can reach as high as 60% in those cases, because the mother’s body hasn’t had time to build antibodies that would offer the baby some protection.
For women with a known history of herpes, the risk is much lower. Doctors typically prescribe suppressive antiviral therapy in the final weeks of pregnancy and may recommend a cesarean delivery if active lesions are present at the time of labor. Women who acquire a new herpes infection during the third trimester may also be offered cesarean delivery due to the possibility of prolonged viral shedding.
Living With Herpes
Genital herpes is a manageable condition. Outbreaks tend to become less frequent and less severe over time, especially for HSV-1 genital infections. Daily suppressive antiviral therapy can reduce both the frequency of outbreaks and the likelihood of passing the virus to a partner. Episodic treatment, where you take medication only when an outbreak starts, is another option that shortens the duration and severity of symptoms.
The stigma around herpes often causes more distress than the virus itself. Given that the majority of adults carry at least one form of HSV and most don’t know it, the gap between how common herpes is and how people perceive it remains wide. A positive test doesn’t change your health in a dramatic way for most people, but it does give you information you can use to protect partners and, if relevant, plan for a safer pregnancy.