Friday, 31 August 2012

Human papillomavirus (HPV)

Human papillomavirus (HPV) is a virus of the papillomavirus type. HPVs infect only the keratinocytes of the skin or mucous membranes. Most HPV infections cause no symptoms in most people.

There are more than 30 to 40 types of HPV that are typically transmitted through sexual contact. Some may cause genital warts, although most cause no symptoms at all. There are other types of HPV virus - classed as "high risk" - that are different from the ones that cause genital warts, and can progress to precancerous lesions as well as invasive cancers. Nearly all cases of cervical cancer are caused by HPV. 

HPV is recognised as an almost-exclusively sexually transmitted infection. It is very rare for prenatal infection to occur from mother to child, or for other methods of transmission – such as shared objects – to occur.

Despite these risks, most HPV infections of this type do not cause disease, with the vast majority of infections being short lived and having no long term significance; around 70% are gone within one year, and 90% with two. However in some cases - around 5% to 10% - there is a risk of developing precancerous lesions of the cervix, which can lead to the development of cervical cancer. This can happen over the course of 10 to 15 years, and as such allows ample time to detect and treat these lesions, but can result in invasive surgery that will cause a loss of fertility.

Signs and Symptoms

There are over 120 different types of HPV, 30 to 40 of which are sexually transmitted. Around 15 are known to be “high risk” carcinogenic types that may lead to the development of cervical cancer.

Depending on the type of HPV virus present, symptoms can include common warts (2, 7), plantar warts (1, 2, 4, 63), flat warts (3, 10, 8), anogenital warts (6, 11, 42 and 44), anal lesions (6, 16, 18, 31, 52, 58), genital cancers (16, 18, 31, 45, 33, 35, 39, 51, 52, 56, 58, 59, 26, 53, 66, 68, 73, 82), oral papillomas (6, 7, 11, 16, 32), orophryngeal cancer (16), verucous cyst (60) and laryngeal papollomatosis (6, 11).

Cervical cancer is usually a sign of infection by HPV at some point, although the virus may no longer be present. It is estimated that around 500,000 new cases of cervical cancer are reported each year, and the vast majority of these cases are caused by prior infection with HPV lead to cervical lesions and invasive cancer. HPV also accounts for a smaller but not-insignificant number of other cancers, including anal cancer, vulvar cancer, vaginal cancer, and penile cancer, as well as a specific HPV-type head and neck cancer.

Diagnosis and Treatment

Generally a diagnosis is reached through cervical testing in women, commonly referred to as “Pap smears”. Routine pap smears are not uncommon, with many developed nations having specific systems in place to allow women to be tested for HPV infection quickly and easily. This involves taking a smear from the woman’s cervix and checking for abnormal cells that could develop into cancer. If these cells are found, a colposcopy is performed which can involve biopsies as well as the removal of specific abnormal areas, which can prevent these cells from developing into cancer.

There is currently no specific treatment for HPV infection in the developed world, but an estimated 90% of all cases of the virus clear up without complications. It is unknown whether the virus is totally removed by the immune system, or whether it is reduce to undetectable levels, and as such there is some question as to how the virus is spread.


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