Theviral family Papillomaviridae comprises papillomaviruses (abbreviated as PVs). Viruses in the Papillomaviridae family were previously classified together with polyomavirus in the Papovaviridae family which is no longer in use in viral taxonomy for DNA containing viruses. The former Papovaviridae family is now divided into Papillomaviridae family and the Polyomaviridae family. Polyomaviridae family contains viruses whose primary hosts are mammals and birds. Papillomavirus is the only viral genome in the Papillomaviridae family. The papillomaviruses are oncogenic in nature; and this implies that papillomaviruses are cancer-causing viruses. Human papillomavirus (HPV) causes papillomas on the lips as well as on the skin and mucous membranes of infected individuals. When they reach the skin, papillomas are known as warts and verrucae; even though they are benign tumours.
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Papillomavirus also causes infection in non-human hosts such as cattle, rabbit, horse, elephant, dog, and birds. Viruses in this family have a circular dsDNA genome that is devoid of envelope. They are icosahedral in shape, and measure about 55 nm in diameter. Papillomaviruses are also resistant to ether but sensitive to UV light and formalin. The replication site of viruses in this family is the nucleus of their infected host cell and they are released from the host cells they infect through cell lysis. Papillomaviruses induce benign lesions of the skin and mucous membranes in individuals infected by the virus. The lesions produced on the skin are known as warts while lesions produced on the mucous membranes are known as condylomas. Genital warts (which occur on the external genitalia of men and women) and cervical cancer are the two most significant infections caused by the papillomaviruses in humans.
The papillomaviruses are of immense clinical importance because of their ability to initiate the development of cancer in infected individuals. Some of the cancers associated with the papillomaviruses include cancer of the cervix, mouth, skin, urogenital tract, gastrointestinal tract, and cancer of the eyes. HPV is implicated clinically as the causative agent of cervical cancer in women, and the virus has a worldwide distribution. Genital HPV infection is one of the world’s most common sexually transmitted viral infections; and the disease occurs in both men and women with varying prevalence’s and morbidity. Since the contraction of one sexually transmitted disease (STD) in a person can place an individual at a higher risk of acquiring another STD or STD causative agent, the risk of infection with HPV is also high especially in HIV-1-infected persons whose immune system have been suppressed by viral (HIV-1) infection.
The sexual route is the main route of transmission of the HPV disease but vertical transmission from mother to child especially during delivery and transmission through direct contact with infected materials such as sharp objects can also occur. There is no specific antiviral agent for the treatment of the disease; and the skin lesions are usually self-limiting. By being self-limiting in nature, HPV infection usually clears on its own without any formal medical treatment. However, surgery is often considered in some cases of papillomavirus infection especially those infections involving the genitalia.
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