Causes of Anogenital Warts

There is only one cause of anogenital warts and that is the Human Papilloma virus. There are many different types of this virus and over 90% of anogenital warts are caused by HPV6 and HPV11. These two strains of the virus are considered low risk because although they cause this sexually transmitted infection, they do not increase the risk of cancer like other HPV strains.

The virus is spread via skin-to-skin contact and the warts are so called anogenital because they occur in the anal and genital regions. Warts on other parts of the skin do not class as anogenital warts and are usually caused by other human Papilloma viruses. It is thought that the HPV virus gets transferred to another person from an infected person through tiny abrasions of the skin that form during sexual contact. The virus can penetrate through the skin layer and into the mucosal surface of the skin.


You will not notice that you have anogenital warts straight away because the virus goes through a latency period. During this time, it lies on your skin and does not replicate so no warts are formed. Months or even years later, the virus may start to replicate in the mucosal layer and the increase in viruses causes the bumpy warts that appear in the infected area. They tend to form either as solo warts or in clusters around the infected area, creating a cauliflower shape.

So why does our immune system not destroy the virus completely? The virus has a very specific way of protecting itself from the immune system. Viruses cannot live outside of cells so they have to have a host and once they have entered the cell, the insert themselves into our DNA. Therefore, the immune system can’t always recognise the virus. When activated, they then start to multiple within our cells and cause the mucosal layer to change shape, causing clusters of lumpy areas known as anogenital warts.


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