What is HPV?
HPV stands for human papillomavirus. It is the most common sexually transmitted infection in the US. Annually, about 14 million new genital HPV infections occur, and nearly all sexually active men and women will be infected with HPV at some point in their lives.
How many HPV types are there?
There are more than 200 known HPV types, and many more are presently uncharacterized, especially in the oral cavity. HPV types are classified as cutaneous or mucosal types depending on what the HPV infects: either the skin or the mucus. About 40 HPV types are infecting the genital area. Of these 40 mucosal HPV types, they are further characterized as low-risk or high-risk HPV types, based on their association with cancer development. There are at least 14 high-risk HPV types identified so far. HPV 16 and HPV 18 represent approximately 70% of high-risk HPV infections.
What are the symptoms of HPV infection?
In the majority of cases, an HPV infection does not cause any visible symptoms. In healthy individuals, about 50% of new HPV infections are cleared naturally by the body (without any treatment) within 6 months time, and 90% of HPV infections will be cleared within 2 years. Low-risk HPV infection can cause genital warts, and high-risk HPV infection can lead to tumor development in a minority of individuals (<5%). E6 and E7 proteins encoded by high-risk HPV types are oncogenes, they can inactivate tumor suppressor genes p53 and pRb respectively, which initiates the development of a tumor.
How does HPV spread?
HPV is mainly transmitted through sexual contact: vaginal, anal, or oral sex. Upon initiation of sexual activity, about 40% women become positive for HPV infection in 24 months. A small fraction of HPV infection can be transmitted through hand-to-genital or other skin-to-skin contact. It is reported that about 1% of virgins are positive for HPV infection and about 10% virgins reporting non-penetrating sex are positive for HPV infection. Because most incidences of HPV infection are asymptomatic, most people do not know whether they are infected with HPV or not, and only molecular assays can determine the presence of HPV infection. Although the body can clear an HPV infection, a small fraction of HPV remains in the body and dormant. This dormant HPV can be re-activated even 10-20 years later when our body’s immune system is weakened as part of a normal aging process.
How can we prevent HPV infection?
Use of a condom or a dental dam can reduce the risk of HPV infection, but cannot fully protect one from HPV infection, because HPV can infect skin that remains uncovered during sexual activity.
The best way to prevent HPV infection proactively is through an HPV vaccine–before a person becomes sexually active. The FDA-approved Gardasil covers four HPV types: HPV 6, 11, 16, and 18. HPV 6 and 11 are low-risk HPV types, and can cause genital warts; while HPV 16 and 18 are high-risk HPV types, and are responsible for 70% of cervical cancer cases. The HPV vaccine is highly effective in preventing HPV infection as well as the development of genital warts and cervical precancer lesions. However, HPV vaccine is prophylactic, thus it does not provide protection for individuals who are already exposed to HPV. The protection gained from the HPV vaccine is type-specific; it does not provide protection of infection of other HPV types besides these four HPV types.
Ideally, in the future, HPV vaccines are the norm and HPV-associated cancers are diminished; but for those who have already been exposed to HPV, raising awareness, understanding risky behaviors, and HPV screenings are highly recommended.
About the author: Dr. Quinne Feng has her Ph. D. in Biochemistry from The Johns Hopkins University School of Medicine, she did her Postdoctoral Fellow at Whitehead Institute/MIT, then worked at the University of Washington for 15 years as a research scientist and faculty member. She is one of the co-founders at Fidalab and developed an accurate and sensitive screening assay for HPV 16 and 18. Dr. Feng remains a dedicated research scientist, and is passionate about science and how it can improve life and health. Learn more about Fidalab’s Oral Rinse Collection Kit for easy, accurate, non-invasive HPV Screening at http://fidalabus.com