What is HPV?
HPV stands for human papillomavirus. There are a number of different types of the HPV virus and different types can cause different diseases. Some are called high-risk types and may go on to cause cervical cancer, anal cancer and precancerous vulvar and vaginal lesions. Others are low-risk types and can cause genital warts and other diseases.
An HPV infection occurs when the virus enters a type of cell called epithelial cells. These can be found throughout the body including the cervix, vagina and anus. People infected with HPV may not know they have the infection as there are often no symptoms.
How common is HPV?
HPV is a very common virus. Around 80% of sexually active people will be infected with HPV at some point in their lifetime. The highest risk of being infected with the virus is during adolescence and early adulthood. Some people can remain infected with HPV for a long time without developing a disease and they may pass the virus on to those they have sex with during this time.
How is HPV spread?
HPV is mainly passed on through sexual contact but can also be passed from mother to child during birth. Anal- and genital-associated HPV types are primarily transmitted by genital contact, passed from person to person either through sexual intercourse or intimate skin-to-skin contact, including oral sex. Although the use of condoms can reduce the risk of HPV infection it does not provide full protection.
Risk of HPV infection increases with:
- Number of sexual partners
- Frequency of sexual intercourse
- Presence of genital warts on sexual partner
- Failure to use condoms (condoms appear to protect men more than women)
What diseases can HPV cause?
For most people, HPV infection goes away naturally. If it persists in the cervix, cervical cells may begin to change and become precancerous, which could, in time, turn into cervical cancer.
As well as cervical cancer, infection with HPV can lead to other diseases such as anal cancer, genital warts, and precancerous vulvar and vaginal lesions.
Can you be protected against HPV?
You can’t be completely protected against HPV but you can reduce your risk of getting an HPV infection by:
Although the use of condoms can reduce the risk of HPV infection, they will not always protect from it. The virus lives on the skin in and around the genital area and is passed on through skin-to-skin contact and not through bodily fluids. However, condoms help protect against many other sexually transmitted diseases, as well as unplanned pregnancy, so it is still very important to use a condom when planning to have sex.
HPV vaccination can help prevent infection from certain types of HPV and can help protect against some of the types that cause cervical cancer.
Get HPV wiser: the HPV virus
HPV is a non-enveloped double-stranded DNA virus belonging to the Papillomaviridae family that infects human epithelial cells. It is a virus with a protein coat (a capsid) comprised of 72 5-sided capsomeres. Each capsomere is made up of L1 proteins (major) and L2 proteins (minor).
Some HPV types can infect the skin e.g. causing a wart on the hand, whilst others infect mucosal membranes e.g. causing cervical cancer.
HPV is a virus with many different genotypes, which are numbered in order of their discovery. Over 100 different genotypes have been identified, sequenced and classified as high-risk or low-risk. Around 40 of these genotypes infect the anogenital tract.
HPV types that have a high risk of causing cancer, such as 16 and 18, are associated with low-grade anogenital lesions and high-grade anogenital lesions, which may lead to precancers or cancer. Low-risk non-oncogenic types, such as 6 and 11, are associated with genital warts and benign/low-grade cervical lesions.
Get HPV wiser: epithelial cell infection and viral replication
For an infection to occur, the virus has to gain access to the replicating basal cells of the epithelium in the host. This can happen during sexual intercourse or after minor scraping of the skin, when the epithelium can become disturbed (microabrasions), allowing the virus access to the basal layer. The virus sheds its capsid before entering the cell.
As the infected cells of the basal layers replicate and differentiate, they carry the HPV DNA with them. As the cells replicate their own DNA, the virus DNA also replicates in the cytoplasm of the host cell. In the upper layers of the epithelium the viral DNA is encased in the protein capsid. Thus complete HPV viruses are produced, which flake off with the discarded epithelial cells and can then go on to infect other cells or other hosts.