Herpes spreads through direct skin-to-skin contact or contact with saliva from someone who carries the virus. The virus enters your body through moist surfaces like the inside of your mouth, genitals, or eyes, or through tiny breaks in the skin that you may not even notice. You don’t need to see sores on someone to contract it, and many people who pass the virus along have no idea they’re infected.
The Two Types of Herpes Simplex
There are two strains of herpes simplex virus. HSV-1 traditionally causes oral herpes (cold sores), while HSV-2 is the primary cause of genital herpes. But the lines between them have blurred. HSV-1 can spread from someone’s mouth to another person’s genitals during oral sex, and this now accounts for a growing share of genital herpes cases. Both strains behave similarly once inside the body: they infect nerve cells near the initial site, go dormant, and periodically reactivate.
Specific Ways the Virus Spreads
The most common routes of transmission are straightforward physical contact:
- Kissing can transmit oral HSV-1 through saliva or contact with skin around the mouth.
- Vaginal or anal sex spreads HSV-2 (and sometimes HSV-1) through genital skin-to-skin contact.
- Oral sex can move HSV-1 from the mouth to the genitals, or HSV-2 from the genitals to the mouth.
- Skin contact with an active sore anywhere on the body carries the highest risk, but transmission also happens when no sores are visible.
The virus doesn’t travel through blood, and casual contact like handshakes or hugging carries virtually no risk. You also can’t catch it from a toilet seat under normal circumstances. While HSV can technically survive on dry surfaces for anywhere from a few hours to several weeks (longer in low-humidity environments), real-world transmission from objects like towels or shared cups is extremely unlikely. The virus needs a viable entry point, and it degrades quickly outside the body.
Why People Spread It Without Knowing
This is the part most people don’t realize: herpes transmits even when the infected person has no symptoms at all. This is called asymptomatic shedding, and it happens when the virus briefly reactivates and appears on the skin surface without causing visible sores or any sensation.
The frequency of shedding varies dramatically from person to person, ranging from zero to as much as 92% of days tested in some individuals. On average, sensitive lab methods detect HSV-1 DNA in the saliva of carriers about one-third of days tested. At least 70% of people who carry HSV-1 shed the virus from their mouth at least once a month, and many shed it six or more times monthly. HSV-2 sheds from genital and anal skin frequently as well, and more often than genital HSV-1.
This means a partner who has never had a visible cold sore or genital outbreak can still pass the virus to you on any given day. Most new herpes infections come from partners who didn’t know they were shedding.
Transmission Risk Between Partners
If one partner in a heterosexual couple has symptomatic genital HSV-2 and no precautions are taken, the annual transmission rate depends on who carries the virus. When the male partner is the carrier, the uninfected female partner has an 11% to 17% chance of contracting it over a year of regular sex. When the female partner carries HSV-2, the male partner faces a lower annual risk of 3% to 4%.
The difference comes down to anatomy. Genital skin exposure during sex is greater for the receiving partner, and the mucosal surfaces of the vagina and cervix are more susceptible to viral entry than the keratinized skin of the penis.
How Condoms and Antivirals Affect Risk
Condoms reduce the risk of herpes transmission, but they don’t eliminate it because herpes can shed from skin that a condom doesn’t cover. Research shows condoms are significantly more protective for women than for men. In one major study, consistent condom use reduced women’s risk of acquiring HSV-2 by roughly 90%, but provided no statistically significant protection for men. The explanation is that condoms cover the penile skin where the virus sheds, protecting a female partner effectively. But men remain exposed to viral shedding from the vulva and surrounding skin that condoms can’t cover.
Daily suppressive antiviral medication taken by the infected partner also lowers transmission risk substantially. Combining consistent condom use with daily antivirals offers the best available protection for discordant couples, though neither method alone or together reduces risk to zero.
What Happens After Exposure
If you contract herpes, symptoms typically appear within six to eight days, though the incubation period can range from one to 26 days. A first outbreak is usually the most severe and may include painful blisters or sores, flu-like symptoms, and swollen lymph nodes. Some people have such mild initial symptoms that they never realize they’ve been infected.
After the first episode, the virus retreats into nearby nerve cells where it remains for life. It can reactivate periodically, causing recurrent outbreaks that are generally shorter and less painful than the first. The frequency of recurrences varies widely. Some people have several outbreaks a year, others go years without one.
Testing After a Possible Exposure
If you think you’ve been exposed, timing matters for testing. A blood test looks for antibodies your immune system produces against the virus, and these take time to develop. It can take up to three months after exposure for antibodies to reach detectable levels. Testing too early can produce a false negative, meaning the test says you’re not infected when you actually are. If you had a specific exposure you’re concerned about, waiting at least 12 weeks before a blood test gives the most reliable result. A swab test of an active sore, by contrast, can confirm the virus immediately if lesions are present.
Herpes Transmission During Pregnancy
A pregnant person with herpes can pass the virus to their baby, most commonly (85% of cases) during vaginal delivery if the virus is active in the genital tract at the time. The risk level depends heavily on when the infection was acquired.
The highest risk scenario is a new genital herpes infection during pregnancy, particularly in the second half. A first infection means the body hasn’t yet produced antibodies that could offer some protection to the baby. If genital herpes was acquired before pregnancy, the risk to the baby during delivery is much lower because the immune system has already built a response to the virus, and any reactivation during delivery involves less viral shedding. Providers typically manage this risk with antiviral medication in late pregnancy and, when active lesions are present at the time of labor, a cesarean delivery.