Human papillomavirus overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Papillomaviruses are a diverse group of DNA-based viruses that infect the skin and mucous membranes of humans and a variety of animals. Over 100 different human papillomavirus (HPV) types have been identified.
Some HPV types may cause condylomas (skin warts) while others may cause a subclinical infection resulting in precancerous lesions. All HPVs are transmitted by skin-to-skin contact.
A group of about 30-40 HPVs is typically transmitted through sexual contact and infect the anogenital region. Some sexually transmitted HPVs -- types 6, 11, may cause genital warts. However, other HPV types which may infect the genitals do not to cause any noticeable signs of infection.
Persistent infection with a subset of about 13 so-called "high-risk" sexually transmitted HPVs, including types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, and 68 — different from the ones that cause warts — may lead to the development of cervical intraepithelial neoplasia (CIN), vulvar intraepithelial neoplasia (VIN), penile intraepithelial neoplasia (PIN), and/or anal intraepithelial neoplasia (AIN). These are precancerous lesions and can progress to invasive cancer. HPV infection is a necessary factor in the development of nearly all cases of cervical cancer.[1]
A cervical Pap smear with HPV DNA testing is used to detect cellular abnormalities and the presence of HPV. This allows targeted surgical removal of condylomatous and/or pre-cancerous lesions prior to the development of invasive cervical cancer. Although the widespread use of Pap testing has reduced the incidence and lethality of cervical cancer in developed countries, the disease still kills several hundred thousand women per year worldwide. A recently approved HPV vaccine, Gardasil, that blocks initial infection with several of the most common sexually transmitted HPV types may lead to further decreases in the incidence of HPV-induced cancer.[2]
Historical Perspective
The fact that prostitutes have much higher rates of cervical cancer than nuns was a key early observation leading researchers to speculate about a causal link between sexually transmitted HPVs and cervical cancer.[3]
Epidemiology and Demographics
Genital HPV infection is very common, with estimates suggesting that more than 50% of women will become infected with one or more of the sexually transmitted HPV types at some point during adulthood.[4]
Diagnosis
Laboratory Findings
Certain types of sexually transmitted HPVs can cause cervical cancer. Persistent infection with one or more of about a dozen of these "high-risk" HPV types is an important factor in nearly all cases of cervical cancer. The development of HPV-induced cervical cancer is a slow process that generally takes many years. During this development phase, pre-cancerous cells can be detected by annual or semi-annual cervical cytology Papanicolaou screening, colloquially known as "Pap" smear testing.
Prevention
Most people become infected with various cutaneous HPV types during childhood. Papillomaviruses have a sturdy outer protein shell or "capsid" that renders them capable of lingering in the environment for long periods of time. Avoiding contact with contaminated surfaces, such as the floors of communal showers or airport security lines, might reduce the risk of cutaneous HPV infection. Treating common warts soon after they first appear may also reduce the spread of the infection to additional sites.
Genital HPV infections may be distributed widely over genital skin and mucosal surfaces, and transmission can occur even when there are no overt symptoms. Several strategies should be employed to minimize the risk of developing diseases caused by genital HPVs:
References
- ↑ Walboomers JM, Jacobs MV, Manos MM; et al. (1999). "Human papillomavirus is a necessary cause of invasive cervical cancer worldwide". J. Pathol. 189 (1): 12–9. doi:10.1002/(SICI)1096-9896(199909)189:1<12::AID-PATH431>3.0.CO;2-F. PMID 10451482.
- ↑ Lowy DR, Schiller JT (2006). "Prophylactic human papillomavirus vaccines". J. Clin. Invest. 116 (5): 1167–73. doi:10.1172/JCI28607. PMID 16670757.
- ↑ zur Hausen H, de Villiers EM (1994). "Human papillomaviruses". Annu. Rev. Microbiol. 48: 427–47. PMID 7826013.
- ↑ Baseman JG, Koutsky LA (2005). "The epidemiology of human papillomavirus infections". J. Clin. Virol. 32 Suppl 1: S16–24. doi:10.1016/j.jcv.2004.12.008. PMID 15753008. *Note: The authors state on page S17 "Overall, these DNA-based studies, combined with measurements of type-specific antibodies against HPV capsid antigens, have shown that most (>50%) sexually active women have been infected by one or more genital HPV types at some point in time."