HPV is spread through direct skin-to-skin contact or through contact with infected mucus membrane. This way the virus infects epithelial tissues. Simply carrying the virus does not cause inflammation most times.
Therefore, HPV is most commonly transmitted through unprotected genital or anal sex. Condoms reduce the risk of infection but they protect only the area they cover.
Even non-penetrative sexual activity can cause inflammation if there are grazes and the body’s immune system does not react immediately.
HPV can also be transmitted during oral sex especially if there are any grazes.
HPV take advantage of genetic mechanisms of human cells. The viruses cannot develop on their own, so they infect epithelial cells and proliferate with them.