Disease
Human Papillomavirus
Author
Megan Johnson, BIOL 230, Spring 2009
Causative Agents
Human Papillomavirus (HPV) is one of a 100 related viruses out of the genus Papilloma and has a family name of Papillomaviridae. The virus is non enveloped, and has an icosahedral (def) shape capsid. HPV contains double strained circular DNA. Typically they range from 52-55 nanometers (def) in diameter.
Epidemiology
Human Papillomavirus is the most common sexually transmitted disease worldwide. As well as being a STD, HPV is the leading cause of cervical cancer. There are 500,000 new cases of cervical cancer occurring worldwide and 250,000 deaths caused by cervical cancer. In the United States there are 6.2 million new cases of HPV infections each year among teenagers and young adults.
Along with cervical cancer, HPV can cause other cancers and disorders. This virus affects mucous membranes (def). HPV is more prevalent in females, then males and until recently had no known effects on males. Recently HPV has been connected cases of penile and anal cancer. Many teens feel that oral and anal sex does not count as pre- marital sex and with that HPV is now being linked with oral cancers as well. With the increase of oral sex and the HPV contacting with the oral mucous membranes explains the increase with oral cancers. In 2008 there were 3460 cases of vulvar cancer, 2210 cases of vaginal cancers, 1250 cases of penile cancer and 3050 cases of anal cancers in females and 2020 cases in males. Genital warts are non-cancerous disorder caused by HPV.
As well as causing cancer the HPV could cause pre-cancerous changes on the cervix. Three hundred thousand cases of high grade cervical dysplasia (def) and 1,250,000 cases of low grade cervical dysplasia are contributed to HPV infections. The treatment of the patients with these pre-cancerous changes cost an estimated 4 billion dollars in in 2004.
Transmission
The transmission of HPV is by direct skin to skin or skin to mucous membrane contact. Most common types of contact will come from contact of the penis, scrotum, vagina, vulva, or anus. It could also be passed from kissing and touching of the genitals. Condoms do not guarantee protection since areas that may have the virus are not always covered by the condoms. HPV is rarely be transmitted from mother to baby during childbirth, resulting in Recurrent respiratory papillomatosis (RRP). In 2008 there were less then 2000 cases of RRP. RRP is when warts develop on the larynx, nasopharynx, oropharynx, trachea, or esophagus which can cause hoarseness, weak cries, feeding difficulties, and failure to thrive and depending on the size airway obstruction.
Signs and Symptoms
There are more then 100 types of HPV and the symptoms depend on the type of virus present. Some types cause warts that live in mucous membranes. The warts may be raised or flat, pink or flesh colored, and some may even look like cauliflower florets. These may or may not be painful. The warts can be on the cervix, penis, anus, scrotum, groin, thighs, or vulva. Normally there are not any symptoms that the average person would recognize for the types of HPV that cause cancer. The only way to screen for cervical cancer, the cancer caused strictly by HPV, is through a pap smear (def). The HPV will cause changes on the cervix that can only be seen through microscopic evaluation. Smoking tobacco increases dysplasia rates and the doubles the risk of HPV leading from precancerous changes to actual cancer.
Prevention and Treatment
The only way to total prevent HPV is through abstinence, or having intercourse with an uninfected person. Unless two virgins have intercourse only with each other the chances of becoming infected with HPV is about 80%. One way to help prevent transmission is the use of condoms, but as previous mentioned condoms do not cover every surface that could possibly lead to transmission. Gardasil is a vaccine that could prevent four of the most frequently acquired strains of the infection, two of which are high risk and two which are low risk. The vaccine is available at this time for females aged 9-27. Also if there has been any prior exposure to any of the strains covered in vaccine you will get no benefit against those strains. Annual pap smears are the only way to screen for HPV. Along with screening annually if there are abnormalities, paps may be required more frequently. At this time there are no screening tools for penile cancer, anal cancer, and oral cancer caused by the virus.
The treatment of the virus also depends on what the virus causes. Warts can be treated differently depending on the severity of the case. Minor infections can be treated by the patient at home with topical creams. More severe cases should be treated in a physician’s office with stronger medications, such as trichloroacetic acid to burn off the warts. Some warts can with stand this treatment and may need to be surgically removed by laser treatments. Precancerous cells treatment will differ. The Pap smear is a screening tool, and once cells come back abnormal further more diagnostic treatments need to be done to determine the severity of the changes. A colposcopy is the diagnostic tool used to determine where the abnormal cells are coming from and what further treatment needs to be done. The fewer the cell changes, the more conservative the follow up. Some physician’s may choose to do paps more frequently and watch for other changes. If there are more severe lesions they may treat with cryosurgery (def), conization (def) or LEEP (def).
Vaccine Information
Gardasil is the only vaccine available for the prevention of HPV. It is made of inactivated viral-like particles composed of self assembled L1 major capsid protein molecules expressed in yeast (Saccharomyces cerevisiae). The vaccine is a series of three shots given over a six month period of time. The initial injection is given, followed by another in two months and the last four months after the second. All three shots must be given to receive any benefit from the injection and the closer to the recommended schedule the best change of receiving maximum benefit. It is given intramuscularly (def) and is not recommended for women who are pregnant or nursing.
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