Human papillomavirus
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| Human papillomavirus
Template:Taxobox begin placement virus Template:Taxobox group i entry | |
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| Family: | Papillomaviridae |
| Genus: | Papillomavirus |
| Species: | Human papillomavirus |
|} Human papillomavirus (HPV) is a virus which affects humans. Some of its effects are classed as sexually transmitted disease (STD).
Scientists have identified more than 100 types of HPV, most of which are harmless. Some types can produce common skin warts on the hands and feet. About 30 types are spread through sexual contact, of which some types can cause visible genital warts, while others can cause cervical cancer and other genital cancers.
HPV is by far the most common sexually-transmitted infection. It is estimated that 80% of sexually active adults have been infected with one or more genital HPV types at some time.[1] (http://www.hpv.org.nz/pdf/hpvguidelines2004.pdf) The vast majority of infected people suffer no ill-effects and never even know that they have been infected, but yet are able to infect others. The immune system typically clears the virus from the body within a year, after which the person will be immune to that particular HPV type.[2] (http://www2.niaid.nih.gov/Newsroom/Releases/hpv.htm)
HPV is an almost unavoidable, and invisible consequence of sexual activity, and for this reason many countries recommend women have a regular pap smear from the time of first sexual activity, to ensure early detection of cervical cancer.
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Prevention
The American Cancer Society advises that condoms do not protect against HPV. Viral sites may be distributed widely over the pelvic area, and transmission can occur even if there are no visible symptoms. The only effective way to prevent genital HPV infection is to abstain from any sexual activity. Risk factors linked to acquiring HPV include: sex at an early age, and having many sexual partners.
Effects
Common skin warts
Some types of HPV (e.g. HPV 1) cause common skin warts, such as those found on the hands and soles of the feet (plantar wart). These types of HPV do not cause genital warts.
Genital warts
Genital warts (condylomata acuminata or venereal warts) are the most easily recognised sign of genital HPV infection. However, of the 30 types of genital HPV, only two cause visible warts (HPV 6, 11). Many people acquire these viruses but never develop warts.
It is important to note that the types of HPV that cause genital warts are NOT the same types that cause cervical cancer.
Cancer
Some types of HPV (HPV 16,18,31) can cause cervical cancer, anal cancer, head and neck cancers, and cancer of the penis (a rare cancer). These viruses have also been associated with cancers of the head and neck. These tumours often have HPV viral sequences integrated into the cellular DNA. Some of the genes encoded by these viruses are known to act as oncogenes. The viral E6 protein binds to and degrades the cellular protein p53 while the viral E7 protein interferes with the retinoblastoma protein.
A history of HPV infection is believed to be a pre-requisite for a woman to develop cervical cancer. According to the American Cancer Society, women with no history of human papillomavirus (HPV) do not develop cervical cancer. However, most HPV infections do not progress to cervical cancer. If a woman does have abnormal cervical cells, a Pap smear will detect them. It is particularly important for women who have abnormal cervical cells to undergo colposcopy so that precancerous and cancerous lesions can be detected and treated early, if necessary.
HPV types 30 and 40 cause laryngeal carcinoma (a throat cancer).
Research
Currently, in Great Britain a vaccination study is under way. It is targeting the four virus strains that are most often responsible for cervical cancer and for abnormal smear test results. In prior trials, the Gardasil vaccine reduced HPV infections by about 90% and pre-cancerous cells were totally eliminated. It is hoped that the vaccine can be released for medical use in two years.[3] (http://news.bbc.co.uk/1/hi/health/4421823.stm)
External links
- American Social Health Association (http://www.ashastd.org)
- National Cancer Institute (http://cancernet.nci.nih.gov)es:VPH
fr:Condylome ru:Папилломавирус человека de:Humanes Papilloma-Virus