Herpes is a common viral infection caused by the herpes simplex virus (HSV). It produces fluid-filled blisters that break open and crust over, most often around the mouth or genitals. Over 846 million people between ages 15 and 49 are living with genital herpes alone, making it one of the most widespread infections on the planet. The virus comes in two types, and once you have it, it stays in your body permanently, alternating between quiet periods and occasional flare-ups.
Two Types of Herpes Simplex
HSV-1 mostly spreads through oral contact and is the type behind cold sores on or around the mouth. It can also cause genital herpes, usually through oral sex. HSV-2 spreads through sexual contact and almost exclusively causes genital infections. You can carry both types at the same time: an estimated 50 million people worldwide do.
The practical difference between the two goes beyond location. HSV-2 causes significantly more frequent recurrences when it infects the genitals compared to genital HSV-1 infections. So a person with genital herpes caused by HSV-1 will typically have fewer and milder flare-ups over their lifetime than someone with genital HSV-2.
How the Virus Stays in Your Body
After the initial infection, herpes travels along nerve fibers and settles into clusters of nerve cells called ganglia, where it goes dormant. HSV-1 prefers the trigeminal ganglia near the base of the skull, which is why it reactivates on the face, lips, and eyes. HSV-2 favors the lumbar-sacral ganglia at the base of the spine, which is why it reactivates below the waist.
During dormancy, the virus produces almost no viral material and your immune system largely ignores it. Periodically, the virus reactivates, travels back down the nerve fibers to the skin’s surface, and causes a new outbreak or sheds invisibly. Triggers vary from person to person but commonly include stress, illness, fatigue, sun exposure, and hormonal changes. The virus itself is not replicating in a way your body can eliminate permanently, which is why herpes is a lifelong infection.
What an Outbreak Feels Like
The incubation period after first exposure ranges from 1 to 26 days, though 6 to 8 days is typical. The first outbreak is usually the worst. Up to 48 hours before blisters appear, you may notice tingling, itching, or burning at the site. With genital herpes, this early phase can also include fever, headache, and swollen lymph nodes.
Then fluid-filled blisters appear, often in clusters. They break open within a few days, leaving shallow, painful sores that gradually crust over and heal. The entire cycle for a first episode typically takes two to three weeks. Recurrent outbreaks follow the same pattern but are shorter and less severe, often resolving in under a week. Over time, most people experience fewer recurrences per year.
Spread Without Symptoms
One of the most important things to understand about herpes is that the virus can spread even when no sores are visible. This is called asymptomatic shedding, and it accounts for a large share of transmission. Among people with symptomatic HSV-2 infections, the virus was detectable on about 20% of days sampled in a large study published in JAMA. Even among people who had HSV-2 but had never noticed symptoms, viral shedding occurred on 10% of days. Critically, about 84% of shedding days in that asymptomatic group showed no visible signs at all.
This means many people transmit herpes without knowing they carry it. It also means that the absence of sores does not guarantee the absence of risk during sexual contact.
How Herpes Is Diagnosed
If you have an active sore, the most reliable test is a nucleic acid amplification test (NAAT), which detects the virus’s genetic material directly from a swab. This method is highly sensitive (91 to 100%) and nearly 100% specific, meaning false results are rare.
When no sore is present, blood tests that detect antibodies can determine if you’ve been exposed. These tests look for immune responses specific to HSV-1 or HSV-2. However, their accuracy is notably lower. HSV-1 antibody tests have sensitivities ranging from 69 to 99% and specificities between 77 and 98%. HSV-2 antibody tests perform worse, with specificity as low as 57%, meaning a positive result may need confirmation with a follow-up test. For this reason, routine screening of people without symptoms is not universally recommended, and results should be interpreted carefully.
Treatment and Daily Management
There is no cure for herpes, but antiviral medications shorten outbreaks and reduce their frequency. Treatment works in two main ways. Episodic therapy means taking medication at the first sign of a flare-up to speed healing, typically over a few days. Suppressive therapy means taking a daily antiviral to prevent outbreaks from occurring in the first place. Suppressive therapy also significantly reduces, though does not eliminate, the risk of transmitting the virus to a partner.
Starting treatment within 48 hours of symptom onset produces the best results. For people who experience frequent recurrences (roughly six or more per year), daily suppressive therapy is generally more effective than treating each outbreak individually. For those with infrequent recurrences, episodic treatment as needed is a reasonable approach.
Beyond medication, condoms reduce transmission risk, and avoiding sexual contact during active outbreaks provides additional protection. Disclosure to sexual partners, while uncomfortable, allows both people to make informed decisions about risk.
Less Common Forms of Herpes
Herpes does not always appear on the mouth or genitals. Herpetic whitlow is an HSV infection of the fingers, causing painful blisters on the fingertip or around the nail. It can develop when someone touches an active sore and the virus enters through a break in the skin.
Ocular herpes, or herpetic keratitis, affects the eye and is one of the more serious complications. The classic sign is a branching, tree-like ulcer on the cornea visible during an eye exam. It can cause pain, blurred vision, tearing, and light sensitivity. Repeated episodes can lead to scarring and vision loss, so prompt treatment is important. HSV-1 is the usual cause of eye infections.
Herpes and Pregnancy
The most serious complication of herpes is transmission to a newborn during delivery, known as neonatal herpes. The risk varies dramatically depending on timing. A mother who acquires a new genital herpes infection near the time of delivery faces a transmission risk estimated at 25 to 60%, because her body hasn’t yet produced the antibodies that help protect the baby. In contrast, a mother with a pre-existing herpes infection who experiences a recurrence has a transmission risk below 2%, because her antibodies cross the placenta and offer the baby some protection.
For this reason, pregnant women who develop new genital symptoms should be tested promptly, and those with known genital herpes are typically offered antiviral medication in the final weeks of pregnancy to reduce the chance of an active outbreak at delivery.
How Common Herpes Actually Is
Herpes is far more prevalent than most people realize. According to 2024 WHO estimates based on 2020 data, about 520 million people aged 15 to 49 had genital HSV-2 worldwide, and roughly 376 million had genital HSV-1. Oral HSV-1 is even more widespread, with the majority of the global population carrying it, often acquired in childhood through nonsexual contact like a kiss from a family member.
Most people with herpes never receive a diagnosis because they either have no symptoms or have symptoms so mild they go unnoticed. This gap between prevalence and awareness is a major reason the virus continues to spread. If you suspect you’ve been exposed or are experiencing symptoms for the first time, testing with an active lesion provides the clearest answer.