The HPV types that cause warts on the skin and genital region differ from the types that cause cancers. HPV types 16 and 18 are responsible for around 70% of all cervical cancers while types 6 and 11 cause approximately 9 out of 10 cases of genital warts and warty growths in the throat.
Around two thirds of people will have been exposed to HPV within three years of becoming sexually active, regardless of the number of sexual partners. Most infections resolve within two years. However, in about 2 in 100 people infection remains after five years. Persistent infection can cause abnormal changes to cells in the cervix, penis, genital, anal and oral tissues in women and men, which can lead to cancer if left untreated.
It has been estimated that around 1 in 20 cancers worldwide are causes by HPV, including almost all cervical and most anal and mouth and throat cancers.
In New Zealand, cervical cancer is the third most common cause of cancer in women aged 25-44 years. Around 160 women are diagnosed with cervical cancer every year, and around 60 die from the disease. Cervical screening detects abnormalities in the cells of the cervix in many more women, some of whom require invasive treatments to prevent the development of cancer. Māori women are at greater risk than other ethnicities for cervical cancer and cervical changes.
How you get it
HPV is very contagious and can be spread through skin to skin contact, as well as sexual intercourse. Virus can be spread through hand-genital contact, oral sex (mouth-genital contact) and from infected mothers to their newborn baby during the birth process.
As most people do not know when they are infected, an infected person can unknowingly spread the virus to others.
Symptoms and treatment
Generally people have no symptoms of HPV infection, except as genital warts. It is therefore important for all women to undergo regular cervical smear tests, whether they have been vaccinated or not.
If left undetected HPV can lead to cancer, including cervical cancer, anal cancer and cancers affecting the mouth, throat, vulva, vagina and penis. It takes usually about 10-20 years from infection to the development of cancer.
Symptoms of genital warts include raised or flat bumps in the genital areas described as soft, moist or flesh-coloured and often taking a cauliflower shape. These can appear in the weeks or months following infection. In women, warts can appear on the areas inside or surrounding the vagina, cervix and anus. In men, warts can appear on the scrotum, penis and inside or surrounding the anus.
Treatments for genital warts depend on the size, location and severity of the warts, and include creams and solutions that are applied directly onto the skin or infected area. Other types of treatment include burning, freezing, laser or surgical removal of warts. These treatments cannot prevent the genital warts from reappearing.
Symptoms of cervical cancer include bleeding or spotting between menstrual periods, bleeding or spotting after sexual intercourse, bleeding or spotting after menopause, unusual vaginal discharge, persistent pain in the pelvis, or pain during sexual intercourse.
There is no treatment for persistent HPV infection itself, however, abnormal or precancerous cervical cells caused by HPV can be treated. Treatment varies depending on the severity and location of the cell changes, and can range from local removal to radiotherapy, chemotherapy and major surgery.
Most people with HPV infection will clear the virus without any complications. HPV is very common and most men and women will be infected at some point in their lives.
About quarter of people with HPV infection will develop genital warts which can be uncomfortable and embarrassing.
As described, some types of HPV cause cancers. Early detection of cancer is very important. Cancer can spread to the bladder, intestines, lungs and liver and may ultimately be fatal.
Other risk factors for HPV-associated cancer, such as cervical cancer include:
- Early start of sexual activity
- Multiple sexual partners
- Women who don’t participate in regular cervical screening.
- Diet low in fruit and vegetables.
- Family history of cervical cancer
- In New Zealand, women over 40 years of age, and women who are Māori or Pacific
Recent studies in New Zealand have suggested that HPV infection linked to an increased risk of complications during pregnancy.
HPV vaccine is highly effective in preventing infection with four of the most common high risk HPV types; HPV 6, 11, 16, and 18. Since the vaccine became available in New Zealand in 2008, the incidence of genital warts has declined.
The best time for HPV immunisation is prior to any sexual activity. The vaccine produces a better immune response in preteens than older teens.
HPV vaccine is recommended and funded for girls aged 9 to under 20 years. A school-based vaccination programme for girls in year 8 is available in most areas of New Zealand. The vaccine is also funded for people who meet certain other medical criteria.
The vaccine is also recommended, but not funded, for boys from 9 to under 26 years and women aged up to 45 years to prevent recurrence of HPV following colposcopy treatment for cervical abnormalities.
Use of condoms during sexual intercourse is recommended, but cannot completely prevent the spread of HPV.
Having a cervical smear tests every three years, if no abnormalities are present, is the best way to detect changes to the cells of the cervix that may later lead to cancer. Regular cervical smears can reduce a woman’s risk of developing cancer by 90%. Women who have had an HPV vaccine should still undergo cervical screening to detect the rarer HPV types not covered by the vaccine.
Complications of disease
Responses to vaccine
As with any medicine, very rare severe allergic responses (anaphylaxis) can occur following immunisation.