Human papillomavirus (HPV) is a group of over 200 related viruses and is the most common sexually transmitted infection. Whether HPV is “bad” is complicated, as the answer depends on the specific strain involved. Most sexually active people will contract it, but in most instances, the infection causes no harm and resolves on its own. The virus is categorized into low-risk types that can cause warts and high-risk types that can increase cancer risk, making the body’s immune response a key factor in the outcome.
How HPV Spreads and How the Body Responds
Human papillomavirus is transmitted through intimate, skin-to-skin contact. This includes vaginal, anal, and oral sex, as well as non-penetrative genital contact. Because the virus can be spread even when an infected person has no visible symptoms, its prevalence is widespread, and many people acquire it within their first few years of becoming sexually active.
The human body is well-equipped to handle the virus. In over 90% of cases, the immune system naturally clears the infection within one to two years, often without the person knowing they were infected. An infection becomes a concern only when it becomes a persistent or chronic infection, as these long-lasting cases with high-risk strains can cause cellular changes over time. Factors like smoking can impair the immune system’s ability to clear the virus.
Low-Risk HPV Strains and Genital Warts
Low-risk HPV strains do not cause cancer but are responsible for causing benign, or non-cancerous, growths. The most common health issue from these types is the development of genital warts. Two strains, HPV 6 and HPV 11, are the cause of approximately 90% of all genital wart cases.
Genital warts appear as soft, fleshy growths on or around the genital and anal areas, and may be small, flat, bumpy, or have a cauliflower-like appearance. While they can cause discomfort or itching, they are not dangerous and do not transform into cancer. Warts may appear weeks, months, or even years after initial exposure, making it difficult to pinpoint the time of infection.
For individuals with genital warts, several treatment options are available. These include topical prescription creams like imiquimod or podofilox, which can be applied at home. A healthcare provider can also perform procedures to remove the warts, such as cryotherapy (freezing) or surgical removal.
High-Risk HPV Strains and Cancer Risk
A small number of HPV strains are categorized as high-risk because a persistent infection can lead to cancer. There are about 12 to 14 high-risk HPV types, but two of them, HPV 16 and HPV 18, are responsible for the majority of HPV-related cancers. HPV 16 is also strongly linked to most cases of oropharyngeal (throat) and anal cancers.
When a high-risk HPV infection is not cleared, it can cause changes in the cells it infects. Over a long period, typically 10 to 20 years, these abnormal cells can progress into precancerous lesions and then into cancer. Nearly all cases of cervical cancer are caused by high-risk HPV, which is also responsible for a significant percentage of cancers of the vulva, vagina, penis, anus, and oropharynx.
The development of cancer from HPV is a slow process, which is why regular screening is effective at preventing it. The virus infects squamous cells, the thin, flat cells lining the inner surfaces of these organs. For cervical cancer, these cellular changes, known as dysplasia, can be detected through routine tests, allowing for treatment that removes the abnormal cells and prevents cancer from developing.
Prevention and Screening Measures
Managing HPV risks involves two main strategies: prevention through vaccination and early detection through screening. The HPV vaccine, such as Gardasil 9, is effective at preventing infections from the types most associated with cancer (HPV 16 and 18) and genital warts (HPV 6 and 11). Vaccination is most effective when administered before an individual becomes sexually active.
The vaccine is recommended for children around the ages of 11 or 12, but it can be started as early as age 9. Catch-up vaccinations are also recommended for individuals up to age 26 who were not previously vaccinated. For those aged 27 to 45, the vaccine may be an option after a discussion with a healthcare provider. Routine cancer screening remains important after vaccination, as the vaccine does not protect against all cancer-causing HPV types.
Screening tests are used to detect problems caused by high-risk HPV. The Pap test, recommended for women starting at age 21, looks for precancerous cell changes on the cervix. The HPV test detects the presence of high-risk HPV strains and is often recommended for women aged 30 and older, sometimes with a Pap test. These tools allow for the identification and treatment of precancerous conditions, stopping cervical cancer before it starts.