Human papillomavirus (HPV)
What is HPV?
Human papillomavirus (HPV) is a virus that infects the skin, and mucous membranes of the upper respiratory and genital tract. It can exist within its host in an active or latent form. There are over 100 types of HPV. Some types are responsible for common warts (verrucae). Around 40 types can infect the genital tract. Some of these are low-risk types (e.g. HPV 6 and 11) which cause genital warts, while others are high-risk types (e.g. HPV 16, 18, etc.) and are associated with various cancers such as cancer of the cervix, vulva, vagina, anus, penis and throat.
How is HPV spread?
- Common skin warts are transmitted through direct physical contact.
- Genital HPV can occur during vaginal, oral or anal sexual intercourse or genital contact with an infected person.
- HPV infection can also be transmitted from mother to baby in the period immediately before or after birth.
What diseases can HPV cause?
The clinical spectrum of disease ranges from asymptomatic infection, to benign warts, to invasive cancer, depending on the virus type, the route of infection, and the body’s immune response.
Most people have warts at some point in their lives. They are more common in children and young adults and usually clear spontaneously over time.
Genital HPV is the most common sexually transmitted disease worldwide. Risk factors associated with genital HPV infection include younger age at sexual initiation, number of sexual partners, and the sexual history of the partner (number of previous sexual partners). The highest rates of HPV infection occur in the 18-28 year age group. An estimated 80% of sexually active women become infected with at least one strain of HPV by age 50 years.
Most genital HPV infections are asymptomatic and transient. It is estimated that 70% of new genital HPV infections clear within one year, and 91% within two years.
HPV and anogenital warts?
HPVs that do not cause cancer are termed low risk types. Two of these low risk types cause genital warts. HPV types are referred to by number (assigned in the order in which they were discovered). Type 6 and 11 are associated with over 90% of anogenital warts.
Anogenital warts usually first appear as small, painless bumps in, on or around the cervix, vagina, anus, penis or scrotum. They may vary in size and shape and usually appear within weeks or months of sexual contact with an infected person.
They are highly contagious; two-thirds of people who have sexual contact with an infected partner will develop warts. In the United States, it is estimated that approximately 1% of sexually active adults have visible anogenital warts and that at least 15% have asymptomatic infection.
In Ireland, anogenital warts account for approximately 30% of all sexually transmitted infection notifications annually with the largest proportion of cases occuring in young adults in the 20-29 year age group.
How are anogenital warts treated?
Anogenital warts are treated according to their size and location. Specific medications can be applied to the warts: they can be frozen with liquid nitrogen or removed through burning or laser treatment. There is no cure for HPV infection and warts can recur after treatment. However, most anogenital warts eventually heal and disappear even if not treated and, in most people, HPV infection clears in time.
HPV and cancer
HPVs associated with cancer are called oncogenic or high risk types. High risk strains are more persistent than low risk strains.
HPV can infect the cells on the surface of the cervix and damage them, causing their appearance to change. This can lead to the development of precancerous lesions over a number of years. These precancerous lesions are called Grade 2 or 3 cervical intraepithelial neoplasia (CIN) and can lead to cervical cancer. Persistent infection by high-risk strains is detectable in more than 99% of cervical cancers.
In addition to persistent infection with high-risk strains of genital HPV, other co-factors appear to be important in the development of cervical cancer, including cigarette smoking, long-term use of oral contraceptives, multiparity, early age at first delivery, immunosuppression and co-infection with Chlamydia trachomatis or herpes simplex virus type 2.
Other HPV associated cancers
Worldwide, an estimated 85% of anal cancers are attributable to HPV infection, with HPV 16 accounting for the vast majority of them. HPV is also associated with between 20-50% of vulval cancers and 60-65% of vaginal cancers.
The incidence of oropharyngeal cancers is increasing, particularly in the Western world. Much of this increase has been attributed to increases in oropharyngeal HPV infection.
What is the incidence of cervical cancer?
In Ireland in 2007, there were 286 new cases of cervical cancer and 81 women died from the disease. The average age at diagnosis is 46 years and of death is 56 years. Mortality from cervical cancer in Ireland is above the EU-27 and EU-15 average (Eurostat).
HPV is responsible for 5.2% of the cancer burden worldwide. Types 16 and 18 are responsible for over 70% of cervical cancers. Cervical cancer is the second most common cancer in women with an estimated 493,000 new cases in 2002 and 274,000 deaths. Most cases occur in countries without effective screening programmes.
Can HPV infection be prevented?
Individuals can reduce their risk of getting genital HPV infection by changes in sexual behaviour including abstinence from any sexual activity or lifelong monogamy. Reducing the number of sexual partners and the frequency of new partners will also reduce the risk. Condom use reduces but does not eliminate the risk of sexual transmission of HPV.
Can cervical cancer be prevented?
Cervical screening can detect pre-cancerous lesions and cervical cancer at an early stage when treatment can be successful. In countries where there is an organized cervical cancer screening programme there has been a marked reduction in the incidence of invasive cervical cancer.
Ireland introduced a national cervical screening programme in September 2009 for women aged 25-60 years. CervicalCheck - The National Cervical Screening Programme
Two vaccines are currently available which will reduce but not eliminate the risk of cervical cancer. At present the available vaccines target only two oncogenic (cancer causing) HPV types (16 and 18) which account for 70% of cervical cancer risk. Therefore, cervical cancer screening programmes will continue to be important even in vaccinated populations.
The vaccines have been shown to be 99% effective at preventing pre-cancerous lesions associated with HPV strains 16 and 18 in women not already infected with these strains.
Cervarix gives protection against infections caused by HPV strains 16 and 18 (associated with 70% of cervical cancers). Gardasil also protects against infections caused by strains 16 and 18 and in addition covers strains 6 and 11 which cause genital warts. The vaccines do not protect against diseases caused by HPV strains that are already established in an individual. For this reason the vaccine is given before the start of sexual activity.
The vaccines do not contain any live material and so cannot cause infection or disease. There is no thiomersol in the vaccines.
HPV Vaccine Programme
Following a recommendation from the National Immunisation Advisory Committee, that human papillomavirus (HPV) vaccine should be given to 12 year old girls, a routine Health Service Executive (HSE) school HPV vaccination programme, with the quadrivalent vaccine Gardasil, began in May 2010 for girls in the first year of second level school and age equivalent in non second level schools (i.e. those turning 12 years of age in the academic year).
More information on the school vaccination programme is available at http://www.hse.ie/eng/health/immunisation/hcpinfo/schoolproghcp/
HPSC collects data on the uptake of the HPV vaccine.
Where to look for further information:
Further information regarding HPV, cervical cancer and HPV vaccine can be found on the following websites:
National Immunisation Office
CervicalCheck - The National Cervical Screening Programme
National Cancer Registry
Department of Health
Health Products Regulatory Authority
Created: 23 June 2010
Last updated: 20 November 2015