Human Papillomavirus Infection

Human Papillomavirus Infection

Papillomaviruses are common in the animal kingdom, but each virus can only infect a single species. Human papillomaviruses (HPVs) can cause a variety of medical conditions. Many HPVs are sexually transmitted, and this article will discuss only the sexually transmitted HPVs.

Symptoms and Causative Agent

HPVs are non-enveloped DNA viruses that infect cells of the skin and mucous membranes.

Most people who contract human papillomavirus infection (HPV) have no symptoms, and they quickly clear the virus from their bodies. However, in other people certain types of low-risk HPVs cause genital warts. Other HPV types are the main cause of cervical cancer, and are associated with anal, penile, mouth, and throat cancers. These are referred to as high-risk HPVs.

HPV is primarily known for its role in causing cervical cancer. Two strains of the virus – strains 16 and 18 – are estimated to be responsible for 70% of cervical cancer cases, leading to about 500,000 new cases and 270,000 deaths worldwide each year. There are about a dozen other high-risk HPV strains that collectively account for the other 30% of cervical cancers.

HPV is very common: one study showed that nearly 27% of women aged 14-59 tested positive for one or more strains of HPV. Rates for men are likely to be similar. More than 80% of women will have been infected with genital HPV by the time they reach age 50.

Transmission

HPV is transmitted sexually through skin-to-skin contact. Anal, oral, and vaginal sex, as well as genital-to-genital contact, all serve as by means people can transmit the virus. Condoms, because they do not cover all potentially infected or infectable areas, do not reliably block HPV spread, but they clearly offer some level of protection against HPV as well as most other STIs. A person infected with HPV may pass the virus even when he or she has no visible signs of infection.

Treatment and Care

Most HPV infections clear on their own and do not require treatment. When warts develop, physicians can usually remove them with medical treatments or with surgical techniques.  Sometimes warts recur and can become persistent.

Cancer-related complications from HPV and treatment of complications are discussed in the next section. However, regular cervical cancer screening for women is an effective tool in interrupting cervical changes that can lead to cancer. According to the U.S. Preventive Services Task Force:

“The USPSTF recommends screening for cervical cancer in women ages 21 to 65 years with cytology (Pap smear) every 3 years or, for women ages 30 to 65 years who want to lengthen the screening interval, screening with a combination of cytology and human papillomavirus (HPV) testing every 5 years.”

Complications

High-risk HPV infections can cause changes in the cells of the cervix and other areas that may lead to cancers. Found early, the affected tissues can be removed via cryosurgery (freezing off the lesions) or other surgical techniques. If they are not detected and removed, cancer may develop. Common treatments for cervical cancer are removal of some or all of the cervix, removal of any other affected areas such as the uterus and surrounding lymph nodes, and chemotherapy and/or radiation. Surgical intervention at any stage of treatment may lead to complications with pregnancy and childbirth.

Cancers of the vulva, anus, and throat may be treated surgically and/or with chemotherapy and radiation.

Annually (latest data from 2012) about 12,000 new cases of cervical cancer occur in U.S. women. This figure does not include cases of women who are diagnosed with and treated for HPV-related precancerous conditions. About 4000 deaths occur annually in the United States from cervical cancer. About 9000 cases of HPV-related anal and throat cancers in women are reported annually. In men, about 12,000 cases of HPV-related cancers occur per year.

A rare complication of HPV involves transmission of the virus from mother to child: during birth, an infant can be exposed to the virus and develop a condition called Recurrent Respiratory Papillomatosis. Warts may develop in the child’s throat and airway, resulting in breathing difficulties, vocal hoarseness, and swallowing problems.

Available Vaccines and Vaccination Campaigns

The U.S. Food and Drug Administration approved Gardasil (HPV4), a Merck vaccine for four types of HPV, in 2006. The FDA approved another vaccine, Cervarix (HPV2) from GlaxoSmithKline, which protects against two high-risk types of HPV, in 2009. A nine-valent vaccine (HPV9, Gardasil 9) was approved in 2014. All HPV vaccines use just a protein from the shell of certain HPV types: they contain no viral RNA or DNA and so cannot cause disease. The HPV vaccines have been shown to be effective in preventing precancerous cervical changes and precancerous anal changes in women and men caused by high-risk cancer-causing HPV strains. HPV4 and HPV9 additionally offer protection from several low-risk, wart-causing HPV types.

Current U.S. recommendations and guidelines from the Advisory Committee on Immunization Practices for HPV vaccination for females and males are below:

The recommended age for HPV vaccination of females is 11-12 years. The vaccine series can be administered as young as age 9 years. Catch-up vaccination is recommended for females age 13-26 years who have not been previously vaccinated.

ACIP recommends routine vaccination of males aged 11 or 12 years with HPV4 or HPV9. The vaccination series can be started beginning at age 9 years. Vaccination with HPV4 or HPV9 is recommended for males age 13-21 years who have not been vaccinated previously or who have not completed the series. Males age 22-26 years may be vaccinated.

For all adolescents, the vaccine is given as a 2-dose series if the series is initiated before age 15. If the series is begun at age 15, 3 doses of vaccine are given.


Sources and Further Reading

CDC. Cervical cancer statistics. Accessed 04/12/2017.

CDC. HPV and men. Accessed 04/12/2017.

CDC. How Many Cancers Are Linked with HPV Each Year?. Accessed 04/12/2017.

CDC. Recommendations on the use of quadrivalent human papillomavirus vaccine in males — Advisory Committee on Immunization Practices (ACIP), 2011MMWR. 60(50);1705-1708. Accessed 04/12/2017.

CDC. Use of 9 valent human papillomavirus vaccine  — updated HPV vaccination recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR. March 27, 2015. 64(11);300-304. Accessed 04/12/2017.

De Kok, I.M., Habbema, J.D., van Rosmalen, J., van Ballegooijen, M. Would the effect of HPV vaccination on non-cervical HPV-positive cancers make the difference for its cost-effectiveness? Eur J Cancer. 2011; 47:428-435.

GAVI Alliance. Human Papillomavirus Vaccine Support. Accessed 04/12/2017.

Kreimer, A.R., et al. Efficacy of a bivalent HPV 16/18 vaccine against anal HPV 16/18 infection among young women: A nested analysis within the Costa Rica Vaccine Trial. Lancet Oncol. 2011; 12: 862–70

Meites, E., Kempe, A., Markowitz, L.E. Use of a 2-Dose Schedule for Human Papillomavirus Vaccination — Updated Recommendations of the Advisory Committee on Immunization Practices. MMWR Morb Mortal Wkly Rep 2016;65:1405–1408. Accessed 04/12/2017.

RRP Foundation. What is recurrent respiratory papillomatosis? http://www.rrpf.org/whatisRRP.html Accessed 2/5/2016.

U.S. Preventive Service Task Force. Cervical Cancer: Screening. Accessed 04/12/2017.

Villa, L.L. HPV prophylactic vaccination: The first years and what to expect from now. Cancer Letters. 2011; 305:106-112.

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Last update 12 April 2017

Assessment Questions

Human papillomaviruses can cause __________.

  • warts
  • cancers
  • both A and B
  • none of the above

True or false? Human papillomaviruses can be transmitted sexually.

  • True
  • False

HPV vaccines are recommended for __________.

  • boys only
  • boys and girls
  • girls only
  • adults only
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