HPV: The Human papillomavirus

The Human papillomavirus

HPV infection is the most frequently sexually transmitted disease in the world.[1]

Both men and women are carriers of HPV.[2][59] 

In the United States, it is estimated that 10% of the population has an active HPV infection, 4% has an infection that has caused cytological abnormalities, and an additional 1% has an infection causing genital warts.[3][4][59] 

If a female college student has at least one different partner per year for four years, the probability that she will leave college with an HPV infection is greater than 85%.[5][59] 

***

Of the 120 known human papillomaviruses, 51 species and 3 subtypes infect the genital mucosa.[6][7][59]  

Table 1: Classification of Human papillomaviruses [1]

Disease	HPV type
Common warts	2, 7, 22
Plantar warts	1, 2, 4, 63
Flat warts	3, 10, 8
Anogenital warts	6, 11, 42, 44 and others [2]
Anal dysplasia (lesions)	6, 16, 18, 31, 53, 58 [3]
Genital cancers	·         Highest risk:[2]    16, 18, 31, 45 ·         Other high-risk:[2][4]    33, 35, 39, 51, 52, 56, 58, 59 ·        Probably high-risk:[4]    26, 53, 66, 68, 73, 82
Epidermodysplasia verruciformis	more than 15 types
Focal epithelial hyperplasia (oral)	13, 32
Oral papillomas	6, 7, 11, 16, 32
Oropharyngeal cancer	16
Verrucous cyst	60
Laryngeal papillomatosis	6, 11

HPV and Cancer

Worldwide in 2002, an estimated 561,200 new cancer cases (5.2% of all new cancers) were attributable to HPV, making HPV one of the most important infectious causes of cancer.[13][59] 

HPV causes cancers of the throat, anus and penis as well as causing genital warts.[36][37][38][59]

Because the process of transforming normal cells into cancerous ones is slow, cancer occurs in people having been infected with HPV for a long time, usually over a decade or more.[11][12][59] 

High-risk HPV types 16 and 18 are together responsible for over 65% of cervical cancer cases.[8][9][10][59]  

Pap smears have reduced the incidence and fatalities of cervical cancer in the developed world, but even so there were 11,000 cases and 3,900 deaths in the U.S. in 2008.[35][59] 

Type 16 accounts for an even greater majority of HPV-induced vaginal/vulvar cancers,[15][59]  penile cancers, anal cancers and head and neck cancers.[14][17][59] 

HPV-induced Cancers [1]

Sexually transmitted HPVs cause approximately 25% of cancers of the mouth and upper throat.[13][16][59] 

In the United States, HPV is expected to replace tobacco as the main causative agent for oral cancer. [15][59] 

HPV and Warts

HPV types that tend to cause genital warts are not those that cause cervical cancer.[20][59] 

Papilloma

Although a wide variety of HPV types can cause genital warts, types 6 and 11 account for about 90% of all cases.[21][22][59]

HPV types 6 and 11 can also cause a rare condition known as recurrent respiratory papillomatosis, in which warts form on the larynx[23][59] or other areas of the respiratory tract.[12][24][25][59] 

HPV and Transmission

Although possible, HPV transmission by routes other than sexual intercourse is less common for female genital HPV infection.[26][27][28][29][30][31][59] 

Odds of oral HPV infection increases with the number of recent oral sex partners or open-mouthed kissing partners.[52][59] Nonsexual oral infection through salivary or cross transmission is also plausible.[53][54][59] 

In 2009, a group tested Australian Red Cross blood samples from 180 healthy male donors for HPV, and subsequently found DNA of one or more strains of the virus in 15 (8.3%) of the samples.[32][59] However, it is important to note that detecting the presence of HPV DNA in blood is not the same as detecting the virus itself in blood, and whether or not the virus itself can or does reside in blood in infected individuals is still unknown. As such, it remains to be determined whether HPV can or cannot be transmitted via blood.[32][59] This is of concern, as blood donations are not currently screened for HPV.[33][34][59]

HPV Prevention and Diagnosis

Methods of prevention include sexual abstinence, condoms, vaccination and microbicides.[59]

Two vaccines are available to prevent infection by some HPV types: Gardasil, marketed by Merck, and Cervarix, marketed by GlaxoSmithKline. Both protect against initial infection with HPV types 16 and 18.[46][59] The Gardasil vaccine also protects against HPV types 6 and 11, which cause 90% of genital warts.[45][59]

The vaccines provide little benefit to women having already been infected with HPV types 16 and 18.[39][41][59]  For this reason, the vaccine is recommended primarily for women not yet having been exposed to HPV during sex.[40][59] 

In most countries, they are approved only for female use, but are approved for male use in countries like USA and UK.[59] 

In 2010, 49% of teenage girls in the US got the HPV vaccine, while in comparison around 67% of teens received shots for meningitis and DPT vaccine.[42][59]

Cervical cancer screening recommendations have not changed for females who receive HPV vaccine.[41][59]  Without continued screening, (Pap smear) the number of cervical cancers preventable by vaccination alone is less than the number of cervical cancers prevented by regular screening alone.[43][44][55][59] 

There is no consensus as to whether anal Pap smear screening for anal cancer might benefit those engaging in anal sex.[17][18][19][59] 

The Centers for Disease Control and Prevention says that male "condom use may reduce the risk for genital human papillomavirus (HPV) infection" but provides a lesser degree of protection compared with other sexual transmitted diseases "because HPV also may be transmitted by exposure to areas (e.g., infected skin or mucosal surfaces) that are not covered or protected by the condom."[47][59]

Female condoms provide somewhat greater protection than male condoms, as the female condom allows for less skin contact.[48][59]

A 2005 review article suggested that several inexpensive chemicals might serve to block HPV transmission if applied to the genitals prior to sexual contact.[49][59] 

Some sexual lubricant brands that use a gelling agent called carrageenan may prevent papillomavirus infection.[50][51][59]

***

There is currently no specific treatment for HPV infection.[20][56][57][59] According to the Centers for Disease Control and Prevention, the body’s immune system clears HPV naturally within two years for 90% of cases.[20][59] However, experts do not agree on whether the virus is completely eliminated or reduced to undetectable levels, and it is difficult to know when it is contagious.[58][59]

Table 1.2: Clearance Rates of High Risk Types of HPV
Months after Initial Positive Test	8 Months	12 Months	18 Months
% of Men Tested Negative[1]	70%	80%	100%
% of Women Tested Negative[2]	50%	75%	97%

Updates / Related

World Health Organization Says Two-Thirds Of World's Population Has Herpes / Medical Daily / October 29, 2015
Could the HPV Vaccine Treat Warts? / LiveScience/ September 4, 2015
STD-Detecting Condoms: UK Teens Invent A Condom That Glows In The Dark Around STIs / Medical Daily / June 23, 2015For HPV vaccine, one dose goes a long way / news.sciencemag.org / June 9, 2015
How Can You Get HPV? Oral Sex and French Kissing Might Give You The Virus, Especially If You're A Smoker / Medical Daily / November 12, 2014

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[50] Buck CB, Thompson CD, Roberts JN, Müller M, Lowy DR, Schiller JT (July 2006)."Carrageenan is a potent inhibitor of papillomavirus infection". PLoS Pathogens 2 (7): 671–680. doi:10.1371/journal.ppat.0020069. PMC 1500806. PMID 16839203.Some, but not all, carrageenan-containing over-the-counter sexual lubricant gels we tested were extremely effective for blocking the infectivity of an HPV16 reporter pseudovirus in vitro. These results raise the possibility that use of such lubricant products, or condoms lubricated with carrageenan based gels, could block the sexual transmission of HPV. However, in the absence of clinical efficacy data, it would be inappropriate to recommend currently available products for use as topical microbicides.
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1)Lee JW, Berkowitz Z, Saraiya M (2011). "Low-Risk Human Papillomavirus Testing and Other Nonrecommended Human Papillomavirus Testing Practices Among U.S. Health Care Providers". Obstetrics & Gynecology 118 (1): 4–13.doi:10.1097/AOG.0b013e3182210034. PMID 21691157.
2.) Saslow D, Solomon D, Lawson HW, Killackey M, Kulasingam SL, Cain J, Garcia FA, Moriarty AT, Waxman AG, Wilbur DC, Wentzensen N, Downs LS, Spitzer M, Moscicki AB, Franco EL, Stoler MH, Schiffman M, Castle PE, Myers ER (2012). "American Cancer Society, American Society for Colposcopy and Cervical Pathology, and American Society for Clinical Pathology screening guidelines for the prevention and early detection of cervical cancer". CA: A Cancer Journal for Clinicians 62 (3): 147–72. doi:10.3322/caac.21139.PMC 3801360. PMID 22422631.
3.) Zhao C, Chen X, Onisko A, Kanbour A, Austin RM (2011). "Follow-up outcomes for a large cohort of US women with negative imaged liquid-based cytology findings and positive high risk human papillomavirus test results". Gynecologic Oncology 122 (2): 291–296. doi:10.1016/j.ygyno.2011.04.037.PMID 21601911.
4.) American Society for Colposcopy and Cervical Pathology (2009), Descriptions of New FDA-approved HPV DNA Tests, American Society for Colposcopy and Cervical Pathology.

[56] "HPV Vaccine Information For Young Women". Centers for Disease Control and Prevention (CDC). June 26, 2008. Retrieved 13 November 2009.
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[59] http://en.wikipedia.org/wiki/Human_papillomavirus

http://www.cdc.gov/std/hpv/stdfact-hpv.htm - link to CDC fact sheet
http://cancer.about.com/od/hp1/f/hpvwarts.htm
http://www.womenshealth.gov/publications/our-publications/fact-sheet/human-papillomavirus.html
http://www.mayoclinic.org/diseases-conditions/plantar-warts/basics/causes/con-20025706
http://www.who.int/immunization/topics/hpv/en/

Tables & Graphs

Table 1: Classification of Human papillomaviruses:

[1] http://en.wikipedia.org/wiki/Human_papillomavirus
[2] Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Mitchell, Richard (2007). "Chapter 19 The Female Genital System and Breast". Robbins Basic Pathology (8 ed.). Philadelphia: Saunders. ISBN [1-4160-2973-7.
[3] Palefsky, Joel M.; Holly, Elizabeth A.; Ralston, Mary L.; Jay, Naomi (February 1988)."Prevalence and Risk Factors for Human Papillomavirus Infection of the Anal Canal in Human Immunodeficiency Virus (HIV)–Positive and HIV-Negative Homosexual Men"(PDF). Departments of Laboratory Medicine, Stomatology, and Epidemiology Biostatistics, University of California, San Francisco. The Journal of Infectious Diseases Oxford University Press. Retrieved 2 March 2014.
[4] Muñoz N, Castellsagué X, de González AB, Gissmann L; Castellsagué; De González (2006). "Chapter 1: HPV in the etiology of human cancer". Vaccine 24 (3): S1–S10.doi:10.1016/j.vaccine.2006.05.115. PMID 16949995.

Graph: HPV-induced Cancers:

[1] Parkin DM (2006). "The global health burden of infection-associated cancers in the year 2002". Int. J. Cancer 118 (12): 3030–44. doi:10.1002/ijc.21731.PMID 16404738.

Table 1.2: Clearance Rates of High Risk Types of HPV

[1] Giuliano AR, Lu B, Nielson CM, Flores R, Papenfuss MR, Lee JH, Abrahamsen M, Harris RB (2008). "Age‐Specific Prevalence, Incidence, and Duration of Human Papillomavirus Infections in a Cohort of 290 US Men". The Journal of Infectious Diseases 198 (6): 827–835. doi:10.1086/591095. PMID 18657037.
[2] Steben M, Duarte-Franco E (2007). "Human papillomavirus infection: Epidemiology and pathophysiology". Gynecologic Oncology 107 (2): S2–S5.doi:10.1016/j.ygyno.2007.07.067. PMID 17938014.

Images:

"Cases of HPV cancers graph" by Retroid - en:wiki. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Cases_of_HPV_cancers_graph.png#mediaviewer/File:Cases_of_HPV_cancers_graph.png

"Papilloma 2009 G1" by George Chernilevsky - Own work. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Papilloma_2009_G1.jpg#mediaviewer/File:Papilloma_2009_G1.jpg

"Papilloma Virus (HPV) EM" by Author: Unknown photographer/artistSource: Laboratory of Tumor Virus Biology - NIH-Visuals Online# AV-8610-3067. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Papilloma_Virus_(HPV)_EM.jpg#mediaviewer/File:Papilloma_Virus_(HPV)_EM.jpg