An HPV infection causes changes to the cells of the cervix, creating abnormalities; it affects the DNA in the cells, meaning any new cells created will also be abnormal. HPV attacks the basal cells of the cervix (these are specific cells found in skin that reproduce new skin cells) . These abnormalities can result in the production of damaged and disorganised cervical cells that cannot function correctly.
Four out of five (80%) women are infected with genital HPV at some point in their lives without ever knowing they have been infected because HPV is usually cleared (without treatment) by the body's immune system, with 80% of cells healing within two years (see pathway 1 in the figure below) .
However, a small percentage of women do not clear the infection and it can remain 'dormant' (inactive) or persistent in their bodies, sometimes for many years  . If your immune system doesn't clear the infection and/or the abnormal cells are not removed or monitored, the DNA of the HPV virus can join with the DNA of the epithelial cells, creating cancer cells (see pathway 2 in the figure below). This is why cervical screening and HPV vaccination are important in helping to spot abnormalities and prevent cancer.
We still don't understand why some women are able to clear the infection, while in others the virus may lead to the development of abnormal cells and possibly cervical cancer.
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