Yes, herpes simplex virus (HSV) is a sexually transmitted infection. But the full picture is more nuanced than a simple yes or no, because there are two types of HSV, and one of them spreads through non-sexual contact as well. Globally, over 846 million people between ages 15 and 49 are living with genital herpes, making it one of the most common infections worldwide.
Two Types, Two Transmission Patterns
HSV-2 is straightforwardly an STI. It spreads through sexual contact with genital or anal skin, sores, or fluids from an infected person. About 520 million people globally had genital HSV-2 in 2020.
HSV-1 is more complicated. It mostly spreads through oral contact and causes cold sores around the mouth. Many people pick it up in childhood from a kiss on the cheek or sharing utensils, which has nothing to do with sex. But HSV-1 can also cause genital herpes, typically transmitted through oral sex. An estimated 376 million people had genital HSV-1 infections in 2020. So depending on how it’s transmitted and where it shows up, HSV-1 can be sexually transmitted or not.
STD vs. STI: Why the Wording Matters
You’ll see both “STD” and “STI” used for herpes, and the distinction is worth understanding. An STI is a virus, bacterium, fungus, or parasite transmitted through sexual contact. An STD implies the infection has progressed to cause symptoms or disease. Since many people with HSV never develop visible symptoms, calling it an STI is technically more accurate in most cases. The CDC and most public health organizations now prefer “STI” because the focus is on identifying and managing infections before they cause disease.
Spread Without Symptoms
One of the trickiest things about HSV is that people can pass it along even when they have no sores or symptoms. This is called asymptomatic viral shedding, and it happens on roughly 3% of days for people with HSV-2 who’ve never had a noticeable outbreak. For those who do get outbreaks, the rate is similar, around 2.7% of days. That number sounds small, but over months and years of a sexual relationship, it adds up. Most new herpes transmissions actually happen during these symptom-free periods, because people are less likely to take precautions when nothing looks wrong.
What Outbreaks Look and Feel Like
A first outbreak of genital herpes is usually the worst. It can include clusters of small, painful blisters on or around the genitals or anus that break open into shallow sores. Some people also get flu-like symptoms, including fever, body aches, and swollen lymph nodes. The first episode can last two to four weeks.
Recurrent outbreaks tend to be milder and shorter. Many people notice tingling, itching, or burning in the area before sores appear. Over time, outbreaks typically become less frequent. Some people have one or two recurrences a year; others stop having them altogether. And a significant portion of people with HSV never experience a recognizable outbreak at all.
Testing Has Real Limitations
If you have active blisters or sores, a swab test taken directly from the sore is the most reliable option. But if there’s nothing visible, your provider may offer a blood test that looks for antibodies to the virus. These blood tests have notable drawbacks. After exposure, it can take up to 16 weeks for antibodies to reach detectable levels, so testing too early can produce a false negative. More importantly, the false positive rate for herpes blood tests is much higher than for STIs like chlamydia or gonorrhea. The risk of a wrong result is especially high for people at low risk of infection. This is one reason the CDC does not recommend routine herpes screening for people without symptoms.
Reducing Transmission Risk
Condoms help, but they don’t eliminate the risk entirely because HSV can spread from skin that a condom doesn’t cover. Research shows condom use is highly protective for women, reducing their risk of acquiring HSV-2 by about 90% when used consistently. For men, the protective effect is less clear, likely because the virus can shed from areas of skin not covered by a condom.
Daily antiviral therapy is the other major tool. Taking a daily antiviral medication reduces the rate of HSV-2 transmission to an uninfected partner. This has been studied specifically in couples where one partner has genital HSV-2 and the other doesn’t. Combining daily antivirals with consistent condom use offers the strongest protection. However, suppressive therapy has not been studied for preventing HSV-1 transmission to partners, or for people with asymptomatic infections who’ve never had a recognized outbreak.
Herpes and Pregnancy
Herpes can pose a serious risk to newborns, though transmission from mother to baby is uncommon when properly managed. The biggest danger is when a mother has an active genital outbreak during delivery, since the baby can pick up the virus while passing through the birth canal. The risk is highest when a woman contracts herpes for the first time during the third trimester, because her body hasn’t had time to build antibodies that would partially protect the baby. In these cases, a cesarean delivery is typically recommended. Women who’ve had herpes before pregnancy and have no active sores at the time of labor usually deliver vaginally without complications.
Some women carry HSV without knowing it, which is why providers pay close attention to any history of genital herpes as a due date approaches. Newborns can also contract HSV after birth from being kissed or touched by someone with active cold sores.