The infection
Genital herpes is caused by herpes simplex virus type 1 or type 2 (WHO, 2025). Type 2 was classically genital and type 1 oral (WHO, 2025), but that has changed: in several countries, genital HSV-1 infections in adults are increasing (WHO, 2024). Once acquired, the virus stays for life in the nerve ganglia and can reactivate, though many infected people never have a recognised outbreak (WHO, 2025).
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Key facts
| Organism | Herpes simplex virus type 1 or 2 |
|---|---|
| Incubation | 2 to 12 days for a symptomatic first episode |
| Unrecognised infection | The majority: most carriers do not know |
| Test | PCR on a swab from a lesion; serology is of little screening value |
| Curable | No: infection is permanent, but treatment controls it |
| Shedding without lesions | Common, and the main route of transmission |
| Pregnancy | Serious neonatal risk, above all with late first infection |
| Prevalence | About 846 million people aged 15 to 49 worldwide in 2020, HSV-1 and HSV-2 combined |
A very common virus
According to WHO estimates for 2020, about 846 million people aged 15 to 49 live with genital herpes, more than one in five in that age group (WHO, 2024). This figure covers both viruses: it adds genital HSV-2 infections (520 million) and genital HSV-1 infections (376 million), with 50 million people having both (WHO, 2024). At least one person every second, or 42 million a year, is thought to acquire genital herpes (WHO, 2024).
One reason the number is so high is that the infection mostly goes unnoticed: it causes few or no symptoms in most cases (WHO, 2024). Even so, more than 200 million people aged 15 to 49 had at least one symptomatic episode in 2020 (WHO, 2024). These are global estimates from mathematical models, and they say nothing about the risk for any one person. Many carriers therefore do not know they have it, and this frequency is the best reason to talk about it without shame: WHO itself notes that genital herpes is under-researched because of the stigma surrounding it (WHO, 2024).
The cold sore virus can also affect the genitals
HSV-1 spreads mainly in childhood, through saliva or contact with the skin around the mouth, and causes oral herpes, including cold sores (WHO, 2024). But someone who has never been infected with HSV-1 can acquire it through sexual contact, and then develop a genital infection in adolescence or adulthood (WHO, 2024). The same virus can therefore cause both a cold sore and genital herpes.
The 2020 estimates show almost no change in the prevalence of genital HSV-2 compared with 2016, while the number of genital HSV-1 infections is higher (WHO, 2024). WHO suggests that the decline in oral infections in childhood, linked to less overcrowding and better hygiene, leaves more adults susceptible to the virus; the authors add that the increase may also partly reflect changes in methods and new data sources (WHO, 2024). Genital HSV-2 remains more serious from a public health point of view: it causes recurrent outbreaks much more often, accounts for about 90% of symptomatic episodes and is associated with a threefold higher risk of acquiring HIV (WHO, 2024).
How it is transmitted
The virus passes through direct contact with a lesion, but above all during asymptomatic shedding, when the virus is present on the mucosa with nothing to see. That is why most transmission occurs outside outbreaks, and why appearance is never a reliable guide. A cold sore can transmit genital herpes during oral sex.
Symptoms
The first episode, when symptomatic, is the most severe: clusters of painful blisters that ulcerate, burning, fever, swollen glands, difficulty passing urine. It lasts one to three weeks. Recurrences are shorter and milder, often preceded by tingling or burning, and generally become less frequent over the years. In many people the infection never announces itself recognisably at all.
Testing
Diagnosis is by PCR on a swab from a lesion, ideally taken at the very start of an outbreak. Serology detects antibodies but does not say where the infection is, and is not recommended as routine screening: a positive result in someone without symptoms generates more anxiety than useful information. It retains a role in specific situations, particularly around pregnancy.
Treatment
Antivirals — aciclovir or valaciclovir — do not eliminate the virus but shorten outbreaks and reduce their severity. They can be taken episodically at the first sign, or continuously where recurrences are frequent or to reduce transmission to an uninfected partner. Continuous suppressive treatment is well tolerated and substantially reduces outbreak frequency.
If left untreated
In healthy adults genital herpes is mainly a physical and psychological burden, sometimes a heavy one. Serious complications concern newborns: neonatal herpes is rare but severe, and the risk is highest when the mother acquires a first infection late in pregnancy. Herpes also increases the risk of acquiring HIV, the ulcers providing a point of entry.
Prevention
- Condoms cut the risk by about 30% with consistent use: they do not cover every area where the virus may be present.
- Avoid sex during an outbreak, from the first tingling until the skin has fully healed.
- Continuous antiviral treatment markedly reduces transmission to an uninfected partner.
- Tell your midwife or doctor in early pregnancy: monitoring and delivery planning depend on it.
After a diagnosis
- Tell your partner: it is the basis of effective prevention, and the infection is far too common to warrant drama.
- Identify your own triggers: tiredness, stress, periods, sun exposure, fever.
- Having a prescription in advance lets you start at the first sign, which changes the length of an outbreak considerably.
- Declare the infection at the first antenatal appointment if you are pregnant.
- If you have symptoms of genital herpes, WHO recommends offering HIV testing (WHO, 2024).
State of research
There is currently no cure for herpes; treatments only relieve the symptoms (WHO, 2024). The authors of the latest global estimates consider new treatments and new vaccines necessary, and WHO supports research on vaccines, treatments and topical microbicides (WHO, 2024); the WHO fact sheet describes no available vaccine (WHO, 2025). A study cited by WHO puts the economic cost of genital herpes at around US$35 billion a year worldwide, in health spending and lost productivity (WHO, 2024). None of this work has produced a vaccine or a curative treatment to date, according to these sources (consulted on 28 October 2026).
Worth remembering
No carrier can guarantee they will not transmit, even with no visible lesion. That is why telling a partner, rather than watching for symptoms, is the real preventive measure.
A little history
The word comes from the Greek herpein, "to creep", and is already found in Hippocrates for lesions that spread across the skin. Genital herpes as a distinct entity was described in 1736 by the French physician Jean Astruc in his treatise on venereal diseases. In 1873 Émile Vidal proved the disease was contagious by inoculating it from one person to another; in 1919 Löwenstein transmitted the virus to the rabbit cornea, demonstrating that it was indeed a virus.
It took until the years from 1960 to distinguish two viruses: HSV-1, mostly oral, and HSV-2, mostly genital, a separation established by Karl Schneweis in 1962 and confirmed by André Nahmias and Walter Dowdle in 1968. Aciclovir, discovered in 1974 in Gertrude Elion's team at Burroughs Wellcome and marketed in the early years from 1980, was the first truly selective antiviral: it earned Elion the Nobel Prize in Medicine in 1988. Valaciclovir and famciclovir are its descendants.
The years from 1980 were also a time of moral panic in the United States: in August 1982 Time magazine put herpes on its cover as "today's scarlet letter". AIDS, which appeared the same year, soon pushed that fear into the background — but the shame attached to an extremely common infection dates from then. No vaccine exists yet, despite repeated trials since the years from 1990.
How this differs between countries
This is the infection on this list where countries differ least: nobody screens for it, and the treatment is the same everywhere.
- No screening anywhere. Serological screening of people without symptoms is not recommended in any country: it generates anxiety without demonstrated benefit.
- Reimbursement of antivirals. The main difference is financial: treatment of outbreaks is covered in many countries, continuous suppressive treatment far less often.
- Availability. Aciclovir is on the World Health Organization's essential medicines list and is widely available, including as an inexpensive generic.
- Delivery planning. Guidance on caesarean section after a late first infection varies slightly, but the principle is the same everywhere.
- Neonatal herpes. Reported more often in countries with organised surveillance, which reflects detection rather than a real difference in incidence.
