Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) are two closely related but distinct viruses that cause lifelong infections. HSV-1 typically causes oral herpes (cold sores around the mouth), while HSV-2 typically causes genital herpes. However, both viruses can infect either location, and the line between them is blurrier than most people realize. Here’s what actually matters about each one.
How HSV-1 and HSV-2 Differ
Despite sharing a high degree of genetic similarity, the two viruses behave differently in the body. HSV-1 is mainly transmitted through contact with sores, saliva, or skin around the mouth. Most people pick it up in childhood from a kiss or shared utensil, often without knowing it. HSV-2 is mainly transmitted through sexual contact with genital or anal skin, sores, or fluids.
The practical distinction comes down to where each virus prefers to live. After the initial infection, both viruses retreat into nerve cells and stay dormant. HSV-1 typically settles into the nerve cluster near the ear, which is why it reactivates as cold sores on the lips. HSV-2 prefers the nerve cluster at the base of the spine, reactivating as genital sores. But HSV-1 can absolutely cause genital herpes, usually through oral sex, and this has become increasingly common.
One important difference: when HSV-1 does infect the genitals, it tends to recur far less frequently than genital HSV-2. Suppressive antiviral therapy reduces genital herpes recurrences by 70% to 80%, but many people with genital HSV-1 have so few outbreaks that daily medication isn’t necessary.
What an Outbreak Feels Like
A first outbreak is usually the worst. For genital herpes, it can last two to four weeks. Sores appear, break open and release fluid, then crust over and heal without scarring. Many people also experience flu-like symptoms during this first episode: fever, body aches, and swollen lymph nodes. Oral herpes first outbreaks can be similarly uncomfortable, with painful sores inside or around the mouth.
Recurrent outbreaks are milder and shorter, typically healing within three to seven days. Many people notice warning signs before sores appear: burning, itching, or tingling at the site where the virus first entered the body. Some feel pain in the lower back, buttocks, or thighs. This warning phase is called the prodrome, and it usually shows up a few hours before sores develop. Recognizing it gives you a window to start antiviral medication early, which can shorten the episode.
A significant number of people with herpes, both types, never have noticeable symptoms at all. They carry the virus and can transmit it without ever developing a sore.
How Herpes Spreads
Both viruses spread through direct skin-to-skin contact. You can get herpes from contact with a sore, but also from skin that looks completely normal. This is called asymptomatic shedding, where the virus reaches the skin surface and becomes contagious without causing visible symptoms. Both HSV-1 and HSV-2 are most contagious when sores are present, but transmission in the absence of symptoms is common, especially with HSV-2.
This means a partner who has no visible sores and doesn’t know they’re infected can still pass the virus along. In fact, most new herpes infections come from people who are unaware they carry it. HSV-1 can spread from the mouth to the genitals through oral sex, which is now one of the leading causes of new genital herpes cases in young adults.
In rare circumstances, a mother with herpes can transmit the virus to her baby during delivery, causing neonatal herpes, which can be serious.
Testing and Diagnosis
If you have an active sore, a healthcare provider can swab it and test for the virus directly. This is the most reliable method during an outbreak. Blood tests detect antibodies your immune system produces in response to the virus and can distinguish between HSV-1 and HSV-2. However, blood tests have an important limitation: after exposure, it can take up to 16 weeks or more for antibodies to reach detectable levels. Testing too early after a possible exposure may produce a false negative.
Routine herpes screening is not part of standard STI panels in most settings, partly because positive results in people without symptoms can cause significant anxiety without clear medical benefit. If you’re concerned about a specific exposure or want to know your status, you’ll typically need to request the test specifically.
Reducing Transmission Risk
Condoms lower the risk of herpes transmission but don’t eliminate it, because the virus can shed from skin that a condom doesn’t cover. In one study, consistent condom use (more than 75% of the time) cut HSV-2 acquisition roughly in half: 4.6% of consistent users acquired the virus compared to 8% of those who never used condoms.
Daily suppressive antiviral therapy also reduces transmission to partners. Combining consistent condom use with daily antivirals provides the most significant reduction in risk. Avoiding sexual contact during active outbreaks, when the virus is most contagious, is another straightforward protective measure.
Treatment Options
There is no cure for herpes. Once infected, the virus stays in your nerve cells permanently. But antiviral medications can shorten outbreaks, reduce their severity, and lower the frequency of recurrences.
Treatment works in two ways. Episodic therapy means taking medication at the first sign of an outbreak to speed healing. This works best when started during the prodrome or within the first day of sores appearing. Suppressive therapy means taking a daily antiviral to prevent outbreaks from happening in the first place. This approach is typically recommended for people who experience frequent recurrences and can reduce outbreak frequency by 70% to 80%.
For many people, outbreaks become less frequent over time even without daily medication. The first year after infection tends to produce the most recurrences, and the body’s immune response gradually improves at keeping the virus dormant.
Potential Complications
For most healthy adults, herpes is more of a nuisance than a serious health threat. But there are situations where it becomes medically significant. Herpes keratitis, an infection of the eye caused by either HSV type, is a major cause of blindness worldwide. It usually heals without damaging the eye, but severe or untreated cases can scar the cornea and lead to vision loss.
Neonatal herpes, though rare, is the most dangerous complication. Babies exposed to the virus during delivery can develop serious infections affecting the brain, organs, and skin. People with weakened immune systems are also at higher risk for severe or prolonged outbreaks that may require more aggressive treatment.
Vaccine Development
No approved herpes vaccine exists yet, but research is active. A therapeutic vaccine candidate called mRNA-1608 completed a Phase 1/2 clinical trial in early 2025, testing whether an mRNA-based approach (similar to the technology behind some COVID vaccines) could provide clinical benefit for people already living with recurrent genital HSV-2. Results from that trial will help determine whether larger studies move forward. Several other candidates are in earlier stages of development.