Human papillomavirus (HPV) is the most common Sexually Transmitted Infection (STI). According to the U.S. President’s Cancer Panel and the Centers for Disease Control and Prevention (CDC), nearly 80 million people in the United States are infected with HPV at this time, and about 14 million people become newly infected each year. According to The American Social Health Association, 80% of sexually active individuals in will be exposed to HPV in the United States. The National Health Service (NHS) estimates that 80% of sexually active individuals will be exposed to HPV in the United Kingdom.

Fortunately, 90% of the time, those infected with HPV will clear the infection within two years. For the population with persistent HPV, the virus can develop into cervical, anal, vulvar, vaginal, penile and head and neck cancers. HPV is responsible for approximately 5% of all cancers globally and causes over 26,000 new cases of cancer in the U.S. and over 5,000 new cases of cancer in the UK in every year.

Human papillomavirus (HPV) is a virus transmitted through contact with the skin and mucosal membranes found in the mouth, throat, vagina, cervix, anus and penis. There are over 100 HPV strains that can affect the human body. The vast majority of these viruses affect the skin and cause benign warts. About 40 HPV types are sexually transmitted and about 16 of those strains cause lesions that can progress to cancer. A person can be infected with multiple HPV strains simultaneously.

HPVs can be classified into high-risk and low-risk groups according to the likelihood that an infection by the HPV type can lead to a cancer. The most common high-risk strains are HPV-16 and HPV-18, although types HPV-31, HPV-35, HPV-39, HPV-45, HPV-51, HPV-52 and HPV-58 are also high-risk. Low-risk strains, such as HPV-6 and HPV-11, cause 90% of genital warts; these strains rarely develop into HPV-related cancer and may be linked with benign lesions and/or mild dysplasia. The 2012-2013 U.S. President’s Cancer Panel report showed that 92% of anal cancer is most likely caused by HPV-16 and HPV-18, the HPV types which cause most HPV-related cancers in the United States. Other studies have shown that though HPV-16 is the most common link to anal cancer followed by HPV-18, other types of HPV such as HPV-33 and HPV-73 infections have led to anal cancer.

In the United States, HPV infection causes more than 96% of all cervical cancers, 93% of anal cancers, 64% of vaginal cancer, 51% of vulvar, and 36% penile cancers. HPV also causes 25% of oral and oralpharyngeal cancers with HPV-16 present in 90% of oral HPV-positive tissues. Oral infections with low-risk HPVs can cause Recurrent Respiratory Papillomatosis (RRP), when children develop warts in their throat during birth, which lead to persistent health problems throughout their lives. In the United States nearly 820 children are diagnosed with RRP every year.

Most sexually active people will be infected with at least one type of HPV at some point in their lives. Having just one sex or oral sex partner can expose you to HPV. Although the immune system generally clears an HPV infection within several months to a few years, some infected people may not resolve the infection. The virus can remain in the skin layer and gradually alter cells so that they become abnormal and cancerous usually after a period of years or decades after the initial infection. If one has an HPV infection on their skin and experience a trauma such as a cut, the HPV can cause cell abnormalities deeper in the skin.

Men and women infected with HPV can unknowingly spread the virus as the infection may present no symptoms and infected individuals may not realize that they carry it. Though a condom may help reduce transmission, HPV is spread via skin-to-skin contact through the moist layer of skin and can therefore be passed onto a partner even when a condom is used. Nevertheless, safe sex practices including the use of condoms should still be utilized as a method to reduce the likelihood of transmission.

Precancerous lesions caused by HPV infections are classified into categories according to the severity of cellular abnormality. The same classification system exists for all HPV-caused abnormalities in the anogenital region. These precancerous manifestations are named, depending on the part of the body infected, anal intraepithelial neoplasia (AIN), cervical intraepithelial neoplasia (CIN), penile intraepithelial neoplasia (PIN), vaginal intraepithelial neoplasia (VaIN) and vulvar intraepithelial neoplasia (VIN). These classifications can be grouped into three levels indicating various stages of cellular abnormalities. AIN I, AIN II, and AIN III denote the level of cellular  abnormality for precancerous cells in the anus with stage I being the least, and stage III the most, severe lesion. AIN III is also called carcinoma-in-situ and can develop into invasive anal cancer if not treated.

There is no cure for HPV infections, although the vast majority of people’s immune systems are able to control the virus. People diagnosed with HPV precancerous lesions can be treated for the infection and monitored before the lesions become cancerous. HPV-associated lesions sometimes require repeat treatments over a period of months or years. Screening for these abnormal cells is one of the most effective means to prevent the development of anal and other HPV-associated cancers.

Screening is a vital component in preventing HPV-associated cancers. The importance of screening has proved extremely effective in decreasing the prevalence cervical cancer, another HPV-associated cancer. In the United States, incidence rates for cervical cancer fell by 57% between 1975 to 2007, with a similar decline in deaths from the disease.  This translates to a difference of nearly 10,000 lives saved per year, adjusted for the growing size of the population. The primary reason for the decline is better screening practices and methods, including regular check-ups and cervical pap smears. HPV-associated cancers in other sites, such as the anus, remain on the rise in part due to a lack of widespread screening protocols. In the United States, sexually active women are recommended to have cervical Pap smears and digital rectal exams (DREs) during regular gynecological visits to test for HPV-associated lesions and other abnormalities. There is a growing trend in the medical community to call  DREs digital anorectal exams (DAREs) to emphasize that the clinician is checking the anus as well.  Experts believe this exam is an effective method for detecting anal cancer.

Men are not regularly tested for HPV-related cell abnormalities.HPV, if unresolved by the body’s immune system and left untreated, can eventually cause anal, penile and head and neck cancer in men. Men who have sex with men (MSM) are among those who are most at risk for acquiring anal HPV infection, although men who have sex with women (MSW) can also develop anal HPV infection. More recently, the medical community is improving efforts to screen MSM for anal HPV, but these efforts are inconsistent and vary among different practitioners and municipalities. People at risk should be examined using DAREs, anal Pap smears, or high-resolution anoscopies (HRA), which is a procedure using a high resolution magnifying instrument called an anoscope to identify abnormal cells (similar to a colposcope used to identify cervical abnormalities).

If you believe you are at risk for anal HPV infection or have anything that seems abnormal, you should ask your doctor if he or she can implement appropriate screening procedures. Ask your doctor about these procedures. Do not expect your doctor to suggest these for you. If diagnosed with an abnormal cervical or anal pap smear, additional tests can be performed to determine whether the patient has a high-risk or low-risk lesion. These include a laboratory HPV DNA test to determine of the range of HPV strains the infected individual has been exposed to. Post-diagnosis, men and women who have an HPV infection should carefully monitor their body and obtain regular check-ups.

Vaccines are available that protect against the most common cancer-causing strains of the virus, HPV-16 and HPV-18. These two HPV strains cause 75% of cervical carcinomas and are also highly prevalent in vulvar, vaginal, penile and head and neck cancers associated with HPV.  It is estimated that up t0 85% of anal carcinomas are caused by HPV-16. There are currently two vaccines on the market that are approved by the Federal Drug Administration (FDA) called Gardasil and Cervarix with different indications. These vaccines are administered in three doses, all of which are required for them to be most effective.

Gardasil was approved by the FDA in 2006 and became the first vaccine on the market to protect against HPV. Gardasil is indicated to prevent cervical, anal, vaginal, and vulvar pre-cancer and cancer in genital warts in women. It is also approved for the prevention of anal precancer and cancer and genital warts in men.   The FDA recommends Gardasil for women and men between the ages of 9 and 26, preferably before sexual activity. In addition to protecting against the high-risk strains HPV-16 and HPV-18, Gardasil also protects against low-risk strains HPV-6 and HPV-11, which cause the vast majority of genital warts.  A study currently under consideration before the FDA shows that the vaccine is also effective in preventing most cases of anal pre-cancer.

The other HPV vaccine, Cervarix, was approved by the FDA in 2009, and is recommended for females between the ages of 9 and 25. Cervarix does not protect against HPV-6 and HPV-11, but is effective against high-risk strains HPV-16 and HPV-18 for the prevention of cervical cancer and precancer. Cervarix is not approved for men as it has never been studied for efficacy in preventing precancer and warts in men. Gardasil is approved for preventing anal cancer and anal warts in both men and women. A study showing Gardasil is effective in preventing HPV-associated anal disease in men was presented before the FDA’s Vaccine and Biological advisory committee on November 17, 2010.This organization also presented testimonyat the hearing. The FDA approved the vaccine for men and women for the prevention of anal precancer and cancer on December 22, 2010. Dr. Karen Midthun, Director of the FDA’s Center for Biologics Evaluation and Research (CBER), stated in December that the vaccine “as a method of prevention is important as it may result in fewer diagnoses and the subsequent surgery, radiation or chemotherapy that individuals need to endure.”

The data submitted to the FDA illustrated that preventing infection by HPV-16 and HPV-18 would lead to significantly reduced rates of anal precancer and cancer, as many cell abnormalities are caused by these HPV types. It has been suggested, although not proven in studies, that these vaccines will also prevent certain types of HPV-associated head and neck cancers. The FDA recommends that the indicated populations exposed to HPV, or currently infected with the virus, should still be vaccinated if they are in the recommended age bracket. The body can be exposed to more than one strain at any given time and the vaccination will work to prevent cancer caused by the other types. Patients should urge their providers to permit access to the vaccines if they fall within the recommended age range. It is recommended that women and men who are sexually active continue to be monitored by their clinician for precancerous lesions post-vaccination. Such individuals should be tested for the presence of disease as the vaccines do not prevent pre-existing infections nor do they protect against other less common high-risk HPV strains.