Herpes is a common, lifelong infection caused by the herpes simplex virus (HSV). There are two types. HSV-1 usually causes oral herpes (cold sores or fever blisters on or around the lips), and HSV-2 usually causes genital herpes, although either type can infect the mouth or the genitals. Typical symptoms are small, painful blisters that break open into sores, crust over and heal. Many people have no symptoms at all and never know they carry the virus.
Herpes is very common. In the United States, about 47.8% of people aged 14 to 49 have HSV-1 and 11.9% have HSV-2, according to the CDC. There is no cure, but antiviral pills shorten outbreaks, prevent most recurrences when taken daily and lower the risk of passing the virus to a partner. For most healthy adults, herpes is a skin condition to manage, not a danger to life.
Key takeaways
- Herpes is caused by HSV-1 or HSV-2. Both stay in the body for life, hidden in nerve cells, and can reactivate.
- Most infections cause no symptoms or very mild ones. The virus can still spread when no sores are visible.
- The best test is a PCR swab of a fresh sore. Blood tests detect antibodies, not active infection, and low positive results can be false.
- Aciclovir, valaciclovir and famciclovir treat outbreaks. Daily suppressive therapy cuts recurrences by 70% to 80% and lowers transmission.
- Herpes matters most for newborns, people with weak immunity and anyone with eye or brain symptoms, which need urgent care.
What is herpes simplex?
Herpes simplex viruses belong to the same family as the viruses that cause chickenpox and shingles. After a first infection through the skin or a mucous membrane, the virus travels along a nerve and settles in a cluster of nerve cells (a ganglion), where it stays dormant. From time to time it travels back to the skin, causing a new outbreak or being released without symptoms.
HSV-1 and HSV-2: what is the difference?
- HSV-1 is usually caught in childhood or young adulthood through contact with saliva. The WHO estimates that 3.8 billion people under 50, or 64%, have HSV-1.
- HSV-2 is almost always sexually transmitted and is the main cause of genital herpes. The WHO estimates that 520 million people aged 15 to 49, or 13%, have HSV-2.
- HSV-1 now causes a growing share of genital herpes, through oral sex: a 2025 modelling study estimated 376 million people aged 15 to 49 with genital HSV-1 in 2020.
The type matters for your outlook. According to the CDC, genital HSV-1 recurs much less often than genital HSV-2, and its shedding drops quickly during the first year.
How herpes spreads
Herpes spreads through direct skin-to-skin contact with an infected area: kissing, oral, vaginal or anal sex, and touching a sore. The CDC is clear that it is not spread through toilet seats, bedding or swimming pools.
Asymptomatic shedding
The virus can reach the skin surface without causing any sore. This silent shedding explains why most people catch herpes from a partner with no visible lesion. In a Seattle study of 498 people with HSV-2 who swabbed themselves daily, the virus was found on 20.1% of days in people with symptoms and on 10.2% of days in people who had never had symptoms. The CDC adds that shedding is most frequent in the first 12 months after catching HSV-2.
Who is at higher risk?
Risk rises with the number of sexual partners, sex without condoms and a partner with herpes. Women are infected more often: US HSV-2 prevalence was 15.9% in women and 8.2% in men in 2015 to 2016. Sexually transmitted infections often travel together, so a herpes diagnosis is a good moment to check for HIV, syphilis, chlamydia and gonorrhoea.
Herpes symptoms
Most people never notice their first infection. When symptoms appear, they usually start days to a few weeks after exposure; Cleveland Clinic gives a range of about 1 to 26 days.
The first outbreak
The first episode is usually the longest and most painful. The CDC describes blisters on or around the genitals, rectum or mouth that break into painful sores and can take a week or more to heal, often with flu-like symptoms: fever, body aches and swollen glands. Urination can burn when sores touch the urine, a symptom easily confused with other causes of vaginal burning.
Recurrences and the prodrome
Repeat outbreaks are usually shorter and milder, and they tend to become less frequent over time. Many people feel a warning phase called the prodrome: tingling, itching or burning where sores will appear, hours to a day before. Starting episodic treatment during the prodrome works best.
Look-alikes
Not every bump is herpes. Ingrown hairs and infected hair follicles are frequent mimics; our guide on folliculitis or herpes explains how to tell them apart. Inside the mouth, recurrent ulcers are more often canker sores, which are not contagious.
Oral herpes vs genital herpes
Oral herpes usually shows up as a cluster of small blisters on the edge of the lip, sometimes on the gums or the roof of the mouth. MedlinePlus notes that cold sores normally go away on their own in a few weeks. HSV can also infect the back of the mouth, as explained in our article on throat herpes.
Genital herpes affects the penis, vulva, vagina, cervix, buttocks, anus or inner thighs. Common triggers include illness with fever, stress, fatigue, strong sun on the lips, menstruation and friction. Oral and genital herpes are the same disease in different places: an HSV-1 cold sore can pass to the genitals through oral sex.
Complications of herpes
For most people, herpes stays a skin problem. Complications are rare but important to recognise:
- Neonatal herpes: a newborn infected during birth can develop a skin, eye, brain or whole-body infection (see the pregnancy section).
- Herpes keratitis: HSV-1 infection of the cornea, with a red, painful, light-sensitive eye. An ophthalmology review notes that delayed diagnosis can lead to vision loss. It is not ordinary conjunctivitis and needs an eye doctor.
- Herpes encephalitis: a rare brain infection with fever, confusion, behaviour change or seizures. A review reports mortality as high as 70% without treatment and around 20% even with intravenous aciclovir. HSV can also cause a milder meningitis.
- Higher HIV risk: a meta-analysis of 57 studies found that HSV-2 almost triples the risk of acquiring HIV in the general population (relative risk 2.7), with the highest risk soon after a new HSV-2 infection (4.7).
How herpes is diagnosed
The CDC recommends confirming a suspected diagnosis with a laboratory test, because sores can mislead and the virus type changes counselling.
Swab tests of a sore: PCR and viral culture
The best test is a nucleic acid amplification test (NAAT, usually PCR) on a swab from a fresh blister or ulcer. It is the most sensitive test and tells HSV-1 from HSV-2. Viral culture is less sensitive and misses more cases as the sore heals, so a negative culture does not rule out herpes. Go early, ideally within the first days of an outbreak. The CDC does not recommend swabs when no sore is present.
Blood tests: type-specific IgG serology
A blood test looks for antibodies, which form in the first weeks after infection and last for life. Only type-specific tests based on glycoprotein G should be used. Our serology test guide explains how STI antibody panels work, and our page on the IgG blood test covers this antibody class. The CDC stresses three limits:
- A positive HSV-1 result cannot tell whether the infection is oral or genital.
- A blood test cannot show when you were infected or who passed it on.
- After a recent exposure, antibodies may not be there yet: repeat the test 12 weeks after the presumed date of infection.
Why IgM tests are not recommended
The CDC recommends against HSV IgM testing, so a positive result should not be read as proof of a recent or genital infection. Our article on the IgM blood test explains why IgM is a weak timing marker.
Should everyone be screened?
No. In 2023 the US Preventive Services Task Force reaffirmed a grade D recommendation against routine blood screening for genital herpes in people without symptoms, including pregnant people: the harms, such as false positives and anxiety, outweigh the benefits. The CDC suggests type-specific testing in selected cases: recurrent or unusual genital symptoms with a negative swab, a partner with genital herpes, people with many partners being checked for STIs, and people with HIV.
Herpes test results table
This table summarises what each herpes test result usually means. Wording and cut-offs vary between laboratories, so compare with the range on your own report.
| Test and result | What it usually means | Next step |
|---|---|---|
| Lesion PCR positive for HSV-1 or HSV-2 | The sore is herpes, and the type is known | Treatment; counselling based on the type |
| Lesion PCR or culture negative | Herpes less likely, but a late swab can miss it (culture more often) | Swab a new sore early; type-specific serology if symptoms recur |
| HSV-1 IgG positive | Past HSV-1 infection, oral or genital (the test cannot tell) | Interpret with symptoms; very common in adults |
| HSV-2 IgG positive, index above 3.0 | HSV-2 infection is likely, usually genital | Discuss with your doctor; HIV test advised |
| HSV-2 IgG low positive, index 1.1 to 3.0 | Often a false positive with the common HerpeSelect assay | Confirm with a second test (Biokit or Western blot) |
| HSV IgG negative | No infection, or infection too recent to detect | Repeat 12 weeks after a possible exposure |
| HSV IgM positive | Not reliable: does not prove a recent or genital infection | Ask for type-specific IgG or a lesion PCR instead |
How to read your herpes results
A positive swab from a sore is close to certain. A blood test answers another question: has your immune system ever met this virus?
The index value
Many reports give an index value rather than a yes or no, with cut-offs that depend on the assay. For HSV-2, the CDC warns that the widely used HerpeSelect test is often falsely positive at low index values between 1.1 and 3.0, where its specificity is poor (one study it cites found 57.4%). A low-positive HSV-2 result should be confirmed with a different test before anyone is told they have genital herpes.
Sensitivity, timing and HSV-1
The sensitivity of type-specific HSV-2 tests ranges from 80% to 98%, so a negative result is usually reliable, except in the first weeks after infection; repeat it 12 weeks after a recent exposure. A positive HSV-1 result with no history of genital sores most often reflects oral infection caught in childhood, not genital herpes.
Herpes treatment
Three oral antivirals are used: aciclovir, valaciclovir (a prodrug of aciclovir that needs fewer pills) and famciclovir. According to ChEMBL, aciclovir is activated by a viral enzyme, thymidine kinase, then blocks the viral DNA polymerase. They cannot remove the dormant virus from nerve cells, which is why herpes comes back.
First outbreak
The CDC advises treating every first episode of genital herpes, even if mild. Regimens, each for 7 to 10 days (longer if healing is incomplete), are aciclovir 400 mg three times a day, famciclovir 250 mg three times a day or valaciclovir 1 g twice a day.
Episodic treatment of recurrences
For occasional recurrences, keep a prescription at home and start within one day of the first sore or during the prodrome. CDC options include valaciclovir 500 mg twice a day for 3 days, valaciclovir 1 g once a day for 5 days, aciclovir 800 mg twice a day for 5 days or famciclovir 1 g twice a day for 1 day. For cold sores, MedlinePlus notes that antivirals speed healing and help prevent sores in people who get them often.
Daily suppressive therapy
If outbreaks are frequent or you want to protect a partner, daily treatment is an option: valaciclovir 500 mg or 1 g once a day, aciclovir 400 mg twice a day or famciclovir 250 mg twice a day. According to the CDC, it reduces recurrences by 70% to 80% in people with frequent outbreaks.
Severe disease and resistance
Encephalitis, neonatal herpes and widespread infection are treated in hospital with intravenous aciclovir (5 to 10 mg/kg every 8 hours in adults, per the CDC). Aciclovir-resistant herpes is rare and seen mostly with weak immunity; foscarnet is the treatment of choice, under a specialist.
Living with herpes and telling a partner
A herpes diagnosis often hurts more emotionally than physically. Herpes is extremely common, outbreaks usually fade over the years, and transmission can be greatly reduced.
- Tell a partner before sex, at a calm moment, and explain how you will lower the risk together.
- Avoid sex during outbreaks and the prodrome, when the virus is most present.
- Look after triggers you can control: sleep, stress and sun protection for the lips.
- Talk to your doctor or a counsellor if anxiety or low mood follow the diagnosis.
How to prevent herpes
There is no vaccine yet. Several measures stack up:
- Condoms used every time reduce but do not eliminate transmission, because the virus can shed from uncovered skin.
- Suppressive therapy for the infected partner: in a trial of 1,484 couples, daily valaciclovir 500 mg cut symptomatic genital herpes in the uninfected partner by 75% (4 of 743 vs 16 of 741 on placebo) and overall HSV-2 acquisition by about half (1.9% vs 3.6%).
- No kissing or oral sex with a cold sore.
- Testing for other infections: regular HIV testing and, when indicated, a syphilis RPR test.
Herpes in pregnancy, newborns and people with weak immunity
Pregnancy
Having herpes before pregnancy is reassuring. The CDC estimates the risk of neonatal herpes at under 1% for women with recurrent herpes, but 30% to 50% when a woman catches genital herpes close to delivery. In a Washington State study of 58,362 pregnant women, when HSV was present in the birth canal during labour, caesarean delivery lowered transmission from 7.7% to 1.2%. According to the CDC, doctors:
- Ask every pregnant woman about genital herpes symptoms, including prodromal symptoms.
- Offer suppressive aciclovir 400 mg three times a day or valaciclovir 500 mg twice a day from 36 weeks for women with genital herpes.
- Recommend a caesarean if genital lesions or prodromal symptoms are present when labour starts.
Routine herpes blood screening is not part of standard blood tests during pregnancy, in line with the USPSTF.
Newborns
The WHO estimates about 10 cases of neonatal herpes per 100,000 births worldwide. Babies can also be infected after birth, for example by a kiss from someone with a cold sore. Blisters, fever, poor feeding or unusual sleepiness in a young baby are an emergency.
People with weak immunity
People with advanced HIV, transplants or strong immune-suppressing drugs can have larger, longer and more frequent outbreaks, and are the group in whom aciclovir resistance appears.
When to see a doctor
See your GP or a sexual health clinic for a new genital sore (NHS sexual health clinics offer free, confidential testing and treatment, and you do not need a GP referral), ideally within the first days so it can be swabbed, for frequent outbreaks, or if you are pregnant and have ever had genital sores. Call 999 or go to A&E for:
- Fever with severe headache, stiff neck, confusion, unusual behaviour or a seizure.
- A painful red eye with blurred vision or strong light sensitivity.
- A young baby with blisters, fever, poor feeding or unusual sleepiness.
- Widespread blisters, or spreading sores in someone with weak immunity.
Latest scientific advances in herpes
Vaccines: many candidates, none approved yet
The Herpevac trial of a glycoprotein D vaccine in 8,323 women gave only 20% overall protection against genital herpes. Newer candidates listed on ClinicalTrials.gov include Moderna's therapeutic mRNA-1608 for recurrent genital HSV-2 (NCT06033261, 303 participants, completed in 2025), BioNTech's preventive mRNA vaccine BNT163 (NCT05432583, phase 1) and GSK's HSV immunotherapy (NCT05298254, completed in 2025). We found no peer-reviewed efficacy results yet. For you: condoms and suppressive therapy remain the tools that work.
Pritelivir and a new class of antivirals
Pritelivir is a helicase-primase inhibitor, a new class that still acts on aciclovir-resistant virus. The phase 3 PRIOH-1 trial (NCT03073967, 158 immunocompromised patients) was completed in November 2025, and a 2026 review reports breakthrough therapy designation and priority review for aciclovir-resistant HSV. Gilead is starting a phase 2b trial of GS-1179, a drug of the same class, against valaciclovir in 300 people (NCT07912996). For you: good news first for resistant herpes, perhaps later for longer-acting suppression.
Gene editing aims for a cure
In 2024, a Fred Hutchinson team reported that gene-editing enzymes removed 90% or more of dormant HSV-1 DNA in mouse models of oral infection and up to 97% in genital models, and reduced shedding; high doses caused liver toxicity. Human trials have not started.
USPSTF 2023 and new global estimates
The Task Force kept its grade D recommendation against routine screening, mainly because of false positives. A 2025 WHO-supported study estimated that 25.6 million people aged 15 to 49 caught HSV-2 in 2020, and that about 205 million had genital herpes sores that year; the authors call vaccines critically needed.
Which tests can help?
- A sore right now: a lesion swab for HSV PCR, plus tests for syphilis if your doctor suggests it.
- No sore but past symptoms or a partner with herpes: type-specific HSV-1 and HSV-2 IgG, with confirmation of a low-positive HSV-2.
- A new herpes diagnosis: an HIV test and a broader STI screen; our pages on gonorrhoea testing and chlamydia explain these tests.
- Pregnancy: tell your maternity team about any history of genital sores.
Glossary
- HSV-1 and HSV-2: the two herpes simplex viruses, mostly oral and mostly genital.
- Latency: the dormant state of the virus inside nerve cells.
- Prodrome: tingling, itching or burning that announces an outbreak.
- Asymptomatic shedding: release of virus on the skin without a visible sore.
- PCR (NAAT): a test that detects the virus's genetic material.
- Type-specific IgG serology: a blood test for lasting antibodies against HSV-1 or HSV-2.
- Suppressive therapy: a daily antiviral that prevents outbreaks and lowers transmission.
Frequently asked questions
Is herpes curable?
No. The virus stays in nerve cells for life. Treatment controls it well: outbreaks become shorter and rarer, and transmission drops.
What percentage of the population has herpes simplex 1?
About 47.8% of Americans aged 14 to 49 had HSV-1 in 2015 to 2016, according to the CDC. Worldwide, the WHO estimates 64% of people under 50.
How do you live with herpes 2?
Most people with HSV-2 live normal lives, relationships included. Know your triggers, keep episodic treatment at home or take daily suppressive therapy, tell partners, use condoms and avoid sex during outbreaks.
What are the long-term effects of herpes for females?
For most women, they are recurrent outbreaks and the emotional burden. Herpes matters most in pregnancy, where a new infection close to delivery carries the highest risk for the baby. HSV-2 also raises the risk of acquiring HIV.
How long does a herpes outbreak last?
A first genital outbreak can take a week or more to heal. Recurrences are shorter and milder. Cold sores normally heal on their own within a few weeks.
Can you have herpes and test negative?
Yes. A late swab can miss the virus, and antibodies may take up to 12 weeks to appear. Swab a new sore early, or repeat the blood test after 12 weeks.
Sources
- Workowski KA et al. — Sexually Transmitted Infections Treatment Guidelines, 2021: Genital Herpes — MMWR Recomm Rep, 2021 — cdc.gov
- CDC — About Genital Herpes — CDC, 2024 — cdc.gov
- McQuillan G et al. — Prevalence of Herpes Simplex Virus Type 1 and Type 2 in Persons Aged 14–49: United States, 2015–2016 — NCHS Data Brief, 2018 — cdc.gov
- World Health Organization — Herpes simplex virus (fact sheet) — WHO, 2025 — who.int
- US Preventive Services Task Force — Serologic Screening for Genital Herpes Infection: Reaffirmation Recommendation Statement — JAMA, 2023 — doi.org
- Harfouche M et al. — Estimated global and regional incidence and prevalence of herpes simplex virus infections and genital ulcer disease in 2020 — Sex Transm Infect, 2025 — doi.org
- Tronstein E et al. — Genital shedding of herpes simplex virus among symptomatic and asymptomatic persons with HSV-2 infection — JAMA, 2011 — doi.org
- Corey L et al. — Once-daily valaciclovir to reduce the risk of transmission of genital herpes — N Engl J Med, 2004 — doi.org
- Looker KJ et al. — Effect of HSV-2 infection on subsequent HIV acquisition: an updated systematic review and meta-analysis — Lancet Infect Dis, 2017 — doi.org
- Brown ZA et al. — Effect of serologic status and caesarean delivery on transmission rates of herpes simplex virus from mother to infant — JAMA, 2003 — pubmed.ncbi.nlm.nih.gov
- Belshe RB et al. — Efficacy results of a trial of a herpes simplex vaccine — N Engl J Med, 2012 — doi.org
- Aubert M et al. — Gene editing for latent herpes simplex virus infection reduces viral load and shedding in vivo — Nat Commun, 2024 — doi.org
- Gege C, Kleymann G — Helicase-primase inhibitors as next-generation anti-HSV agents — Expert Opin Ther Pat, 2026 — doi.org
- Gurgel Assis MS et al. — Novel Insights to Enhance Therapeutics With Aciclovir in the Management of Herpes Simplex Encephalitis — J Pharm Sci, 2021 — doi.org
- Cabrera-Aguas M et al. — Infectious keratitis: A review — Clin Exp Ophthalmol, 2022 — doi.org
- AiCuris — Pritelivir for aciclovir-resistant mucocutaneous HSV infections (PRIOH-1, NCT03073967) — ClinicalTrials.gov, 2025 — clinicaltrials.gov
- ModernaTX — mRNA-1608 HSV-2 therapeutic candidate vaccine (NCT06033261) — ClinicalTrials.gov, 2025 — clinicaltrials.gov
- BioNTech — BNT163 prophylactic HSV-2 vaccine (NCT05432583) — ClinicalTrials.gov, 2026 — clinicaltrials.gov
- GlaxoSmithKline — HSV-targeted immunotherapy (NCT05298254) — ClinicalTrials.gov, 2025 — clinicaltrials.gov
- Gilead Sciences — GS-1179 versus valaciclovir in recurrent genital herpes (NCT07912996) — ClinicalTrials.gov, 2026 — clinicaltrials.gov
- EMBL-EBI — ChEMBL: aciclovir (CHEMBL184) and pritelivir (CHEMBL4069597) — ChEMBL, 2026 — ebi.ac.uk
- MedlinePlus — Genital Herpes; Cold Sores — NLM, 2024-2025 — medlineplus.gov
- Cleveland Clinic — Herpes Simplex Virus (HSV): Types, Symptoms and Treatment — Cleveland Clinic, 2025 — my.clevelandclinic.org
- NHS — Genital herpes — NHS, nhs.uk — nhs.uk
- NHS — Cold sores — NHS, nhs.uk — nhs.uk
Further reading
- Throat herpes: symptoms, causes and treatments
- Folliculitis or herpes? How to tell them apart
- Serology test: what an STI panel detects
- Canker sores: causes, symptoms and treatments
- Shingles symptoms: causes, spread and testing
- Human papillomavirus: symptoms, vaccine and tests
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