The infection
Human papillomaviruses are a family of some two hundred known viruses (WHO, 2024), around forty of which infect genital and oral mucous membranes. Low-risk types cause genital warts; high-risk types, chiefly 16 and 18, together cause about 70 to 76% of cervical cancers depending on the estimate (WHO, 2026), and a large share of anal, throat, vulval, vaginal and penile cancers. Infection is so common that it can be regarded as an ordinary event in sexual life: in nine cases out of ten the body clears the virus within one to two years with no consequence.
Key facts
| Organism | DNA virus, about 200 types, around 40 genital |
|---|---|
| Low-risk types | 6 and 11: responsible for 90% of genital warts (CDC, 2021) |
| High-risk types | Mainly 16 and 18: cervical, anal and throat cancers |
| Cleared naturally | About 90% of infections within two years |
| Screening | HPV test on a cervical sample from age 30; self-sampling increasingly offered |
| Treating the virus | Not possible: lesions are treated, not the infection |
| Vaccine | Yes, highly effective; the WHO's priority is girls aged 9 to 14 |
How it is transmitted
The virus passes through simple skin and mucosal contact in the genital area, without penetration. That is why condoms, which do not cover the whole contact area, protect only partly — though they still reduce risk substantially. Transmission through oral sex explains the rise in HPV-related throat cancers. Infection usually occurs in the first years of sexual activity.
Symptoms
In the overwhelming majority of cases there are no symptoms at all. Low-risk types cause warts: small painless growths, single or clustered, on the vulva, penis, scrotum, around the anus or inside the vagina, appearing weeks to months after exposure. High-risk types never cause symptoms: they work silently and are found only by screening.
Testing
There is no validated screening test for men. For women, cervical screening now relies on the HPV test, which is more sensitive than conventional cytology: in most guidelines, cytology every three years from 25 to 29, then an HPV test every five years from 30 to 65. Vaginal self-sampling, now offered in several countries, allows women who do not attend screening to test at home.
Treatment
No treatment removes the virus itself: the immune system does that in most cases. What is treated are the manifestations. Warts are treated with immune-modulating cream, cryotherapy, laser or surgery, with a real risk of recurrence. Precancerous cervical lesions found by screening are either monitored or removed by a simple excision procedure that prevents progression to cancer.
If left untreated
Persistence of a high-risk type over several years can produce precancerous lesions and then cancer, chiefly of the cervix but also the anus, oropharynx, vulva, vagina and penis. The interval between infection and cancer is long, typically fifteen to twenty years (WHO, 2026) — and it is precisely that interval that makes screening so effective.
Prevention
- The WHO recommends vaccinating girls aged 9 to 14 as a priority (WHO, 2026), before sexual activity begins; whether boys are included, and the ages for routine and catch-up doses, are set by each national schedule.
- It works best before first sexual contact, but remains worthwhile afterwards.
- The vaccine does not replace screening: it does not cover every high-risk type.
- Condoms reduce but do not remove the risk, since transmission is by skin contact.
After a diagnosis
- A positive HPV test is not a cancer diagnosis: it records the presence of a virus that usually clears on its own.
- Keep to the follow-up interval given: what matters is persistence of the virus, not its presence.
- It is impossible to date infection: a positive result says nothing about a partner's fidelity.
- Partners need neither treatment nor HPV testing; cervical screening should simply continue as normal.
Worth remembering
A positive HPV result never reveals when or from whom the infection came. The virus can lie dormant for years, and finding it in a settled relationship is not evidence of anything.
A little history
Genital warts were described by Greek and Roman physicians — the word "condyloma" comes from the Greek for "knob" — and already linked to sexual relations. In 1842, in Verona, Domenico Rigoni-Stern noticed that cervical cancer was almost unknown among nuns and common among married women and prostitutes: the first epidemiological evidence of a sexually transmitted cause. In 1907 Giuseppe Ciuffo showed that warts are transmitted by a cell-free filtrate, hence by a virus.
The screening smear, developed by George Papanicolaou between the 1920s and the 1940s, pushed back cervical cancer wherever it was applied, without the cause yet being known. It was Harald zur Hausen who, against the prevailing view that blamed the herpes virus, proposed papillomaviruses in 1976, then isolated HPV 16 in 1983 and HPV 18 in 1984 from cervical tumours: between them they cause 70% of cases. He received the Nobel Prize in 2008.
The vaccine relies on "virus-like particles", empty shells with no genetic material, a technique developed in 1991 by Ian Frazer and Jian Zhou in Brisbane, alongside American teams. Gardasil was approved in 2006, Australia launched the first national programme in 2007, and the nine-valent vaccine arrived in 2014. In 2020 the WHO adopted a strategy to eliminate cervical cancer; since 2022 it accepts that a single dose protects.
Country by country
The medicine is the same everywhere, but access, prevention programmes, what is free of charge and which services are responsible differ completely. Each country below has its own page.
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