Herpes spreads through direct skin-to-skin contact with someone who carries the virus, even when they have no visible sores. There are two types: HSV-1, which typically causes oral herpes (cold sores), and HSV-2, which typically causes genital herpes. Both can infect either location, and both spread in ways that surprise most people.
How HSV-1 Spreads
HSV-1 transmits mainly through contact with the virus in sores, saliva, or skin surfaces in and around the mouth. Kissing is the most common route, but sharing utensils, lip balm, or razors can also pass the virus when sores are present. Most people pick up HSV-1 during childhood from a relative’s kiss, often without ever realizing it.
HSV-1 can also cause genital herpes when someone with an oral infection performs oral sex on a partner. This has become an increasingly common cause of new genital herpes cases, particularly among young adults. The virus doesn’t distinguish between body parts. It infects wherever it makes contact with a mucous membrane or a tiny break in the skin.
How HSV-2 Spreads
HSV-2 transmits during sex through contact with genital or anal surfaces, skin, sores, or fluids from someone who carries the virus. Vaginal, anal, and oral sex can all serve as routes of transmission. The virus enters through mucous membranes (the moist lining of the genitals, anus, or mouth) or through microscopic breaks in the skin that you wouldn’t notice.
The greatest risk of catching HSV-2 is during contact with active sores, but this is actually not when most transmission happens, simply because people tend to avoid sex when they have visible symptoms. The more common scenario is transmission from skin that looks completely normal.
Asymptomatic Shedding: The Hidden Risk
The reason herpes is so widespread is that the virus periodically surfaces on the skin without producing any symptoms, a process called asymptomatic shedding. During these episodes, the virus is present on the skin in quantities large enough to infect a partner, yet the carrier feels nothing and sees nothing unusual.
Shedding frequency depends on how long someone has been infected. During the first six months after infection, the virus sheds on roughly 20% to 40% of days. Over time, that frequency drops to about 5% to 20% of days. That still means the virus can be present on the skin several days each month, with no warning signs. This is why someone who has “never had an outbreak” can still pass herpes to a partner without knowing they carry it.
Transmission Rates Between Partners
In couples where one person has genital herpes and the other doesn’t, the risk of passing the virus isn’t equal in both directions. In one well-known study of monogamous heterosexual couples, about 17% of female partners caught the virus from an infected male over the study period, compared with roughly 4% of male partners catching it from an infected female. Women are more susceptible because the genital mucous membrane area exposed during sex is larger.
Prior immunity matters too. Women who had never been exposed to either type of herpes had an annual acquisition rate of about 32%, while women who already carried HSV-1 antibodies had a rate closer to 9%. Existing HSV-1 antibodies appear to offer partial, though far from complete, protection against HSV-2.
Transmission During Pregnancy and Birth
A pregnant person can pass herpes to their baby during vaginal delivery if the virus is active in the birth canal. The risk depends heavily on timing. A first-ever herpes outbreak during the third trimester, when the body hasn’t yet built antibodies, carries roughly a 33% chance of transmitting the virus to the newborn. A recurrent outbreak during delivery drops that risk to about 3%, because the parent’s existing antibodies cross the placenta and offer the baby some protection.
Neonatal herpes is rare but serious, which is why providers screen for herpes history late in pregnancy and may recommend a cesarean delivery if active lesions are present at the time of labor.
Ways You Cannot Get Herpes
Herpes requires direct contact with infected skin or mucous membranes. You won’t catch it from toilet seats, swimming pools, bedding, or towels. The virus dies quickly once it leaves the body. Casual contact like handshakes or hugs doesn’t pose a risk either, unless an active sore on one person’s skin directly touches broken skin on another person.
How to Reduce Transmission Risk
Condoms provide meaningful but incomplete protection. One large study found that consistent condom use reduced the risk of women acquiring HSV-2 from a male partner by roughly 90%. Protection for men acquiring the virus from a female partner was less clear in the data, likely because herpes sores can appear on skin not covered by a condom.
Daily antiviral medication taken by the infected partner also lowers transmission risk. The CDC notes that a daily dose of the antiviral valacyclovir decreases HSV-2 transmission in couples where one partner is infected. When combined with condom use, the overall risk drops substantially, though it never reaches zero.
Avoiding sexual contact during active outbreaks is the simplest and most effective step. Prodromal symptoms, the tingling or burning sensation that often precedes visible sores, are a signal that the virus is active and contagious.
Testing and Detection Timeline
If you think you’ve been exposed, standard blood tests look for antibodies your immune system produces in response to the virus. These antibodies take time to develop. After exposure, it can take up to 16 weeks for current tests to detect infection. Testing too early can produce a false negative.
If a sore is present, a swab test can identify the virus directly and give results much sooner. This is the most reliable way to confirm herpes during an active outbreak. If you notice an unusual sore, getting it swabbed before it heals gives the clearest answer.