Strains of Human Papillomavirus (HPV)

Human papillomaviruses (HPV) are extremely common DNA viruses that only infect humans.

Papilloma is a word that means a small wart-like growth on the skin or mucous membrane. There are many types of papillomaviruses - even some that your pet may get. For example, dogs get canine papillomaviruses. So if you are wondering, “can you get HPV from animals?” the answer is no. HPV is only a human skin infection.

HPV is thought to be the most common sexually transmitted infection (STI) in the world. Almost every person will have HPV at some point in their lives.

There are over 150 types of HPV that live on the body and only a small number of types (ie. high-risk HPV) cause problems by changing cells from normal to abnormal.

HPV infect skin cells. Infection with low-risk HPV types can cause external genital warts. Low-risk HPV (lrHPV) – HPV 6 and HPV 11 cause approximately 90% of genital warts and are rarely associated with pre-cancer or cancer of the lower genital tract.

Warts on other parts of the body, such as the hands, are caused by different types of HPV. Contact with these warts does not seem to cause genital HPV warts.

Infection with high-risk HPV (hrHPV) types that are not cleared by the immune system can cause cervical cancers and a significant proportion of cancers of the anus, oropharynx, vagina, vulva and penis. HPV cancers take many years to develop.

The 14 most cancer-causing HPV types include types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66 and 68. Types 16 and HPV 18 are most commonly associated with development of cancer, together accounting for about 70% of invasive cervical cancers. However, not all infections with HPV 16 or 18 do progress to cancer. In addition, HPV 16 is strongly associated with anal cancer and throat cancer.

Current research indicates that high-risk HPV changes the host (human) cell but its growth needs additional triggers to cause cancer.

Most HPV infections are transient and thought to clear naturally before they cause any health problems.