Human Papillomavirus (HPV)
Imagine a virus that most sexually active people will encounter at some point in their lives. For the majority, it passes without causing any noticeable problems. For others, it may appear as a small wart on the skin, a growth around the genitals, or, years later, contribute to the development of cancer.
This is human papillomavirus (HPV), one of the most common viral infections in humans. Although HPV is frequently discussed in the context of cervical cancer, its effects extend far beyond the cervix. Depending on the type of virus involved, it can cause harmless skin growths, genital warts, recurrent growths in the respiratory tract and several types of cancer in both women and men.
What is HPV?
Human papillomavirus is a family of viruses that infect the skin and mucous membranes, including those of the genital tract, mouth and throat. More than 200 HPV types have been identified, with approximately 40 preferentially infecting the genital area.
HPV is most commonly transmitted through intimate skin-to-skin contact, particularly during sexual activity. Vaginal and anal sex can transmit the virus, but penetration is not necessary. Genital to genital contact and oral sex can also transmit HPV. Other HPV types spread through contact with infected skin and cause ordinary skin warts.
Most HPV infections cause no symptoms, which means someone can carry and transmit the virus without knowing they have it. Infection is not evidence of promiscuity, poor hygiene or infidelity. Even someone who has had only one sexual partner can acquire HPV.
Beyond sexual contact, additional physiological and lifestyle factors influence how HPV is managed by the body. Male circumcision, for example, has been shown to reduce the rates of acquiring and transmitting high risk HPV types, while also offering protection against penile cancer. For oral exposure, using barrier methods like condoms or dental dams during oral sex can reduce transmission risk.
Not all HPV types are the same
HPV has different types which cause different diseases. Broadly, genital HPV types can be divided into low risk and high risk groups according to their potential to cause cancer.
Low-risk HPV: The types that cause warts
HPV types 6 and 11 are responsible for approximately 90% of anogenital warts(growths around the penis, vulva, vagina, anus or surrounding skin). They can be flat, raised or cauliflower-like in appearance and may occur singly or in clusters.
Although genital warts are usually benign, they can cause discomfort, itching, bleeding or psychological stress.
Other HPV types cause common warts on the hands, fingers and feet. Plantar warts(on the soles of the feet), can become painful when walking.
HPV types 6 and 11 can also cause recurrent respiratory papillomatosis, a condition in which benign(no cancerous) growths develop in the respiratory tract, in the larynx(voice box). These growths can affect the voice and, in severe cases, obstruct the airway. They may recur even after treatment.
Importantly, the HPV types that cause most genital warts are different from the types responsible for most HPV related cancers.
High risk HPV: When an infection can lead to cancer
Other HPV types are classified as high risk, or oncogenic, because persistent infection with these types can cause precancerous changes and finally cancer.
HPV types 16 and 18 are important. Together, they account for approximately 70% of cervical cancers worldwide. Other high risk types include HPV 31, 33, 35, 39, 45, 51, 52, 56, 58 and 59.
These infections are associated with cancers of the cervix, anus, penis, vulva, vagina and oropharynx. The oropharynx includes structures such as the tonsils and the base of the tongue.
Having a high risk HPV infection does not mean that someone has cancer or will inevitably develop it. The majority of HPV infections resolve or become undetectable without causing serious disease. The greatest concern is persistent infection with an oncogenic type.
How can a virus cause cancer?
Cancer develops when changes in a cell's genetic material alter the mechanisms that normally regulate its growth, division and survival. These changes may arise from inherited genetic variations, errors during DNA replication, environmental exposures, lifestyle related factors or some infections.
When a high risk HPV infection persists, viral proteins can interfere with the normal controls that prevent cells from dividing uncontrollably. Over time, affected cells may accumulate further abnormalities and progress through precancerous changes to invasive cancer.
Viral persistence is not determined by the virus itself, external cofactors play a significant role in impairing the immune system's ability to clear the infection. Tobacco smoking is a major contributor, causing impaired mucosal immunity in both the reproductive tract and the throat and significantly increasing the likelihood that high risk HPV will persist and progress to cancer. Long term use of oral contraceptives and high parity (having given birth to multiple children) are other cofactors.
HPV is therefore an example of an oncogenic infection: an infection capable of contributing to cancer development. It is not the only infectious agent associated with cancer, but it is among the most important because vaccination can prevent many of the diseases it causes.
HPV and HIV Co-Infection
HIV progressively weakens the immune system when it is not well controlled. Because the immune system is responsible for controlling HPV infection, people living with HIV, especially those with advanced immunosuppression, are more likely to experience persistent HPV infections, extensive genital warts(which may undergo malignant transformation to become cancerous) and recurrent disease after treatment.
Can the body eliminate HPV on its own?
Yes. One of the most reassuring facts about HPV is that the immune system controls or clears most infections naturally.
The World Health Organization estimates that approximately 90% of HPV infections are eliminated by the body within two years. This frequently happens without symptoms or specific treatment.
However, there is an important distinction between treating HPV itself and treating the conditions it causes. There is currently no routine medication that eradicates a HPV infection. Instead, healthcare professionals treat problems such as genital warts, precancerous lesions and cancers when they occur.
How is HPV diagnosed?
Diagnosis depends on the type of HPV related disease and the body site affected.
Visible genital warts are usually diagnosed through clinical examination. If a lesion looks unusual, grows rapidly, bleeds or fails to respond to treatment, a biopsy may be necessary to establish the diagnosis and exclude others.
High risk HPV testing is used primarily in cervical cancer screening and follow up. Depending on the screening programme, it may be used alone or alongside examination of cervical cells(a pap smear).
Modern screening guidelines prioritize high risk HPV DNA testing together with traditional Pap smears. For general populations, routine cervical screening typically begins at age 30, whereas for women living with HIV, screening starts earlierat age 25.
There is no routinely recommended general HPV screening test for men, and no approved general screening test for HPV in the mouth or throat. This does not mean men cannot acquire HPV or develop HPV related disease, it means that routine testing strategies are different.
People with symptoms or suspicious lesions should seek clinical assessment.
HPV vaccination: Protection for both girls and boys
HPV vaccination is one of the most effective ways to prevent diseases caused by the virus.
The vaccine trains the immune system to recognise selected HPV types before a person encounters them. Depending on the vaccine used, it protects against high risk types responsible for cancer and low risk types that cause most genital warts.
Girls have historically been the main focus of HPV vaccination programmes because cervical cancer accounts for a substantial proportion of HPV related disease worldwide. Vaccinating girls before exposure to the virus provides strong protection against cervical cancer and reduces the future burden of disease.
However, HPV is not exclusively a women's health issue.
Boys and men can develop HPV related penile, anal and oropharyngeal cancers, as well as genital warts. Vaccinating boys directly protects them against the HPV types covered by the vaccine and also contributes to reducing transmission within the population.
Vaccination schedules have also evolved to make protection more accessible. The World Health Organization (WHO) now recommends a single dose HPV vaccine schedule for girls and boys aged 9 to 20 as an effective alternative to multidose regimens.
Vaccination works best before exposure to HPV, which is why it is routinely recommended during early adolescence. It does not treat an infection that is already present, and vaccination does not replace recommended cervical cancer screening.
In Kenya, HPV vaccination has been incorporated into the national immunisation programme. While Kenya’s public routine immunization program currently targets 10 year-old girls to maximize the impact against cervical cancer within public health budgets, boys can still receive the vaccine.
Condoms can reduce the risk of HPV transmission but cannot eliminate it because the virus can infect skin not covered by a condom. Vaccination remains a key preventive measure.
To sum it all
For most people, HPV is a temporary infection that causes no lasting harm. For others, it can cause troublesome warts or, when certain high risk types persist and contribute to the development of cancer.
The good news is that much of this disease is preventable. Vaccination, appropriate screening, timely evaluation of suspicious lesions and effective management of conditions that weaken the immune system can all make a difference.
HPV should neither be treated as a reason for shame nor dismissed as harmless. Understanding the virus allows us to approach it with reassurance, awareness and prevention.
For HPV related conditions' images please click here Warning: Some images are graphic.
Sources
- World Health Organization. Human papillomavirus and cancer.
- Centers for Disease Control and Prevention. Human Papillomavirus (HPV) Infection: STI Treatment Guidelines.
- Centers for Disease Control and Prevention. Anogenital Warts: STI Treatment Guidelines.
- New York State Department of Health AIDS Institute. Prevention and Management of Human Papillomavirus Infection in Adults With HIV.
Ministry of Health, Kenya. National Cervical Cancer Elimination Action Plan 2025–2030.
Image source shutterstock/ Marries Stopes kenya