Science Fair Project Encyclopedia
Scientists have identified more than 100 types of HPV, most of which are harmless. About 30 types are spread through sexual contact. Some types of HPV that cause genital infections can also cause cervical cancer and other genital cancers.
Like many STDs, genital HPV infections often do not have visible signs and symptoms. One study in the USA sponsored by the National Institute of Allergy and Infectious Diseases (NIAID) reported that almost half of the women infected with HPV had no obvious symptoms. People who are infected but who have no symptoms may not know they can transmit HPV to others or that they can develop complications from the virus.
The only way to prevent getting an HPV infection is to avoid direct contact with the virus, which is transmitted by skin-to-skin contact. If one's sexual partner has warts that are visible in the genital area, one should avoid any sexual contact until the warts are treated. Transmission can occur if there are no visible warts. Studies have not confirmed that male latex condoms prevent transmission of HPV itself, but results do suggest that condom use may reduce the risk of developing diseases linked to HPV, such as genital warts and cervical cancer.
Genital warts (condylomata acuminata or venereal warts) are the most easily recognized sign of genital HPV infection. Many people, however, have a genital HPV infection without genital warts.
Common skin warts
Some types of HPV (HPV 16,18,31) can cause cervical cancer, anal cancer, 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.
HPV types 30 and 40 cause laryngeal carcinoma.
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.
Currently, in Great Britain is a vaccination study under way. It is targeting the four virus strains that are most often responsable for cervical cancer and for abnormal smear test results. In prior trials, the Gardasil vaccine reduced HPV infections about 90% and pre-cancerous cells were totally eliminated. It is hoped that the jab can be released for medical use in two years.
Human papillomavirus is one of the most common causes of sexually transmitted disease in the United States. For example, health experts estimate that there are more cases of genital HPV infection than of any other STD in the United States. According to the American Social Health Association , approximately 5.5 million new cases of sexually transmitted HPV infections are reported every year. At least 20 million Americans are already infected.
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