What are anogenital warts?
Anogenital warts are common superficial skin lesions in the anogenital area that are caused by human papillomavirus (HPV). They are also called condyloma acuminata, genital warts, venereal warts and squamous cell papilloma.
What is the human papillomavirus?
The human papillomavirus (HPV) is actually a group of double-stranded DNA viruses.
- There are at least 100 different types of HPV; at least 40 can infect the anogenital area. Many others cause warts on other areas of skin.
- At least 75% of sexually active adults have been infected with at least one type of anogenital HPV at some time in their life.
- HPV is incorporated into skin cells and stimulates them to proliferate, causing a visible wart.
- Visible anogenital warts are often easy to diagnose by their typical appearance. They are usually due to HPV types 6 and 11.
- Most do not develop visible warts. However, the infection may show up on a cervical smear. This is known as subclinical infection.
- Some strains of HPV cause anogenital cancer. These strains may not cause visible warts but they remain contagious.
Who gets anogenital warts?
As anogenital warts are sexually acquired during close skin contact, they are most commonly observed in young adults between the ages of 15 and 30 years. They are highly contagious, and occur in equal numbers in unvaccinated males and females. However, they are rare in people that have been vaccinated against HPV in childhood before beginning sexual activity.
What do anogenital warts look like?
Anogenital warts are flesh coloured papules a few millimetres in diameter that may join together to form warty plaques several centimetres across. They may occur in the following sites:
Warts due to the same types of HPV can also arise on the lips or within the oral mucosa.
Normal anatomical structures may be confused with warts. These include:
- Pearly papules (these are in a ring around the glans of the penis )
- Sebaceous glands on the labia (known as "Fordyce spots")
- Vestibular papillae (the fronds found in the opening to the vagina)
How is HPV transmitted?
Visible genital warts and subclinical HPV infection nearly always arise from direct skin to skin contact.
- Sexual contact. This is the most common way amongst adults.
- Transmission is more likely from visible warts than from subclinical HPV infection.
- Oral sex. HPV appears to prefer the genital area to the mouth however.
- Vertical (mother to baby) transmission through the birth canal.
- Auto (self) inoculation from one site to another.
- Fomites (ie from objects like bath towels). It remains very controversial whether warts can spread this way.
Often, warts will appear three to six months after infection but they may appear months or even years later.
How can transmission of warts be reduced?
Transmission of warts to a new sexual partner can be reduced but not completely prevented by using condoms. Condoms do not prevent all genital skin-to-skin contact, but they also protect against other STDs.
Successful treatment of the warts decreases the chance of passing on the infection.
How are genital warts diagnosed?
Genital warts are usually diagnosed clinically.
Biopsy is sometimes necessary to confirm the diagnosis or viral wart or to diagnose an associated cancer.
In some circumstances, researchers and clinicians may wish to confirm the presence or absence of HPV. One commercially available qualitative test for HPV is the COBAS 4800 Human Papillomavirus (HrHPV) Test, which evaluates 14 high-risk (HR oncogenic) HPV types. A negative test excludes high-risk infection.
What is the treatment for genital warts?
The primary goal of treatment is to eliminate warts that cause physical or psychological symptoms such as:
- No treatment.
- Self-applied treatments at home.
- Treatment at a doctor's surgery or medical clinic.
The underlying viral infection may persist after the visible warts have cleared. Warts sometimes re-emerge years later because the immune system has weakened.
To be successful the patient must identify and reach the warts, and follow the application instructions carefully. Available treatments include:
- Podophyllotoxin solution or cream
- Imiquimod cream
- Sinecatechins ointment (Veregen®), which is not available in New Zealand
Treatment at the clinic
- Podophyllin resin
- Trichloroacetic acid applications
- Curettage and scissor or scalpel excision
- Laser ablation
- 5% fluorouracil cream
Experimental therapies for genital warts include:
Genital warts and cancer
The HPV types that cause external visible warts (HPV Types 6 and 11) rarely cause cancer. Other HPV types (most often Types 16, 18, 31, 33 and 35) are less common in visible warts but are strongly associated with anogenital cancer, including:
- Intraepithelial neoplasia of penile, vulval and anal skin
- Invasive squamous cell carcinoma (SCC) of cervix, penis, vulva and anus
HPV also causes some cases of oral and nasopharyngeal cancers.
Only a small percentage of infected people develop genital cancer. This is because HPV infection is only one factor in the process; cigarette smoking and the immune system are also important.
Cervical smears, as recommended in the National Cervical Screening guidelines, detect early abnormalities of the cervix, which can then be treated. If these abnormalities were ignored over a long period, they could progress to cancer.
Several vaccines are available to prevent HPV infection.
- Cervarix is effective against HPV types 16 and 18. Available in many countries for prevention of cervical cancer, it is not subsidised in New Zealand.
- GARDASIL®9 is effective against HPV types 6, 11, 16, 18, 31, 33, 45, 52 and 58, and is funded and recommended in New Zealand for 12 year old girls and boys and up to the age of 26 years. It can be prescribed for older individuals (unfunded).
HPV vaccination is most effective when offered at a young age, before the onset of sexual activity. However, girls that are already sexually active may not have been infected with the types of HPV covered by the vaccine and may still benefit from vaccination. Women that receive HPV vaccine should continue to participate in cervical screening programmes, as about 30% of cervical cancers will not be prevented by the vaccine.
HPV vaccines are also effective in boys. Vaccination of boys is recommended to reduce transmission of HPV to unvaccinated females. It also reduces the incidence of cancers related to HPV infection.
There has been interest in developing therapeutic HPV vaccines for the treatment of genital warts and cervical cancer in those already infected, and for other strains of HPV that are associated with other forms of viral warts.