The infection with human papillomavirus (HPV) is the single most important risk factor for developing cervical cancer and develops only in humans. This is a small virus that presents with more than 100 different types of HPV which infects skin or mucosa. Different types infect only specific sites e.g genital area or skin. Immunisation against HPV started in September 2008 for girls aged 12 to 13 with a catch up for girls up to 18 in the following 3 years. It is however, unlikely to alter the rates of smear abnormalities for many years.
You should be aware that smoking can make clearing HPV from the body less effective and can make clearance of minor smear abnormalities slower and less efficient. For this reason stopping smoking may be advised by your GP, practice nurse or staff in the colposcopy clinic.
Human papilloma virus is an extremely common virus that is almost always introduced by sexual intercourse and it is usually only transient. More than 8 out of 10 adult men and women have had the infection at some time in their lives, usually in their teens or twenties. However, most people clear this infection spontaneously with no long-term effects. However 5% of women will have abnormal smears, 1-2% will develop pre-cancerous cells (CIN) and a tiny minority of these progress to get cervical cancer. The HPV types commonly linked with cervical cancer and pre-cancer cells are called high risk (or oncogenic).
High risk types of HPV are detected in almost all cervical cancers and persistent infection with high risk HPV is the single most important factor in the development of CIN and of invasive cancer. Of the over 150 HPV viruses, the main types responsible for changes to the cervix are types 16,18,31,33 and 45. HPV 16 is the most prevalent type being found in about 70% of cervical cancers and HPV 18 the next most prevalent. Of those women who have a persistent high risk HPV infection, fewer than 10% would develop cervical disease if this is not detected and treated. Whilst cervical intra-epithelial neoplasia (CIN) is easily treated conservatively, at present there is no specific treatments for HPV infection itself.
Not all HPV types are linked to cervical cancer and those types are called "low risk". Some of these types are responsible for the presence of warts on the vulva or the anus. If a woman has these then her partner would also need examination and possible treatment. Usually a topical cream or burning of warts with laser or diathermy is all that is needed.
HPV testing has been introduced to help identify those women who have minor abnormalities and need further testing with colposcopy. The test applies for the same reason to women who are having follow up post treatment. The test is taken in exactly the same way as a cervical cytology (smear) test and sometimes can be done on the same sample without having to have a second examination.
Although HPV is transmitted through sexual activity it is not a sexually transmitted disease that the time of infection is certain. It is possible the virus to remain dormant for years and under certain conditions that the immune system of the woman will allow it can reveal its presence through an abnormal pap test. HPV infection is almost certain that everybody who is having sexual relationships will get infected by the virus sooner or later and will not present any manifestations unless her or his immune system allows them to do so. Even the use of condoms can not protect entirely from HPV infection. Therefore there is no blame to attach to the current or any other partner of the past. Some abnormal smears with mild changes may not even be due to HPV but most abnormal smears are due to the effects of HPV on the cervix.
There are two vaccines currently available and both are clinically effective against persistent HPV 16 & 18 infection. This provides protection against just over 70% of high risk types of HPV and associated CIN. The vaccine is offered in three doses in school girls and populations studies have shown impressive results at the decline of cervical intraepithelial neoplasia (CIN) in countries that already follow vaccination programmes. It needs to be given before any HPV infection and seems to offer long term protection. When these young women enter the screening programme it will be important that they continue to be screened, as not all cervical precancerour will be prevented by vaccination alone.Return