How the most common sexually transmitted infection became a leading cancer killer.
If you want to point a finger at factors that cause cancer, viruses don't immediately come to mind as a leading perpetrator. But, after environmental and lifestyle factors, infectious diseases are a leading cause of cancer and the human papillomavirus (HPV) is a prime suspect.
HPV is one of the most ubiquitous of all cancer-causing viral infections. It has a particular affinity for cells on the skin and in mucous membranes where they affect the cell's genetic instructions and can make them behave badly. Most of the time HPV is booted out by the body’s immune system, but sometimes the virus can cause some of your cells to transform into benign, precancerous or cancerous tumors.
Certain HPV types have been implicated in a growing list of cancers that affect both men and women, most notably cervical cancer. If estimations are correct, 80% of men and women have been exposed to HPV before the age of 50; HPV infection has enormous public health implications that cannot be ignored.
How do HPV infections affect the body?
There are 100 different types of HPV and more than 30 are considered sexually transmitted infections. HPV can cause a range of diseases affecting the throat, larynx, tonsils, mouth, penis, vagina, cervix and anus. Some types are more likely to cause cancer (high-risk) and some never will (low-risk). Low-risk HPV types are responsible for external skin growths such as common, flat or plantar warts on hands and feet, and venereal warts (condyloma), in or on the vagina, penis and anus.
What makes HPV infections dangerous?
High-risk HPV types are more inclined to cause cancer, but not always and not necessarily right away. Seemingly harmless infections acquired during adolescence and young adulthood can linger for decades, assaulting cells repeatedly over time, sometimes developing into cancer, sometimes not. There are 15 high-risk HPV types that cause cervical cancer; 70% of cervical cancers are caused by HPV types 16 and 18 alone.
How do you get HPV?
People can become infected through oral, vaginal or anal sex, through skin-to-skin, genital-to-genital and genital-to-mouth contact with an infected person. Although HPV is typically acquired during anal and vaginal intercourse with an infected partner, penetration is not necessary. People can also become infected when they are just "fooling around."
What are some HPV-associated cancers?
Almost 90% of anal cancers, 40% of vulvar, vaginal and penile cancers; 25% of mouth; and 35% of throat cancers are caused by HPV. Some research is also looking into the role of HPV in certain types of prostate, lung and breast cancer. But of all the HPV-associated cancers, cervical cancer is the most burdensome. Almost 100% of cervical cancers are caused by HPV, killing 270,000 women worldwide every year. Although not all infections with high-risk HPV will cause cancer, there is no way to know when and if it will happen.
How do you know you have HPV?
That's the tricky part. You probably won't, not without testing. And even then, tests are not able to detect all HPV types. If you are looking for symptoms there are few to none. Some lesions are flat and practically invisible and you can unknowingly come in contact with infected cells on a partner who might not be aware they are infected. If lesions do show up, they will appear a few weeks after contact. You might be able to see genital warts if they sit on the surface of the skin (can look like a cauliflower). But you might not be able to see anything because infections can be hidden deep in the throat, inside the vagina, on the surface of the cervix or inside the anus.
How do you test for HPV?
HPV-specific tests, while not typically performed during a routine gynecological exam as a screening tool, can detect some HPV types but not all. The HPV test takes a sample of cervical cells and sends it to a lab for analysis. It is usually performed in conjunction with a PAP test, but you may need to ask for the HPV test specifically. Most experts don’t recommend screening women with the HPV test until they have reached the age of 30.
The Pap test can detect abnormal changes on the cervix, which can be caused by HPV, but it can also detect changes caused by other infections and non-infectious factors. The Pap test can detect precancerous and cancerous cells that are most likely caused by one or more of the high-risk HPV types. This test is a major victory for decreasing the rates of cervical cancer because it catches cellular changes in an early, more curable stage. But the Pap test can only saves lives when people actually take the test and take it with some regularity.
Men who have suspicious warts can do a home test that involves wrapping the penis for 2 minutes with a vinegar-soaked rag to see if any areas turn white. Since this isn't an official or perfect test, all lesions should be checked by a healthcare professional.
How is HPV-associated cancer treated?
If abnormal cervical cells are suspicious for cancer, a small sample of the tissue removed during colposcopy - an instrument that magnifies tissue in the vagina and cervix - and examined further under a microscope to rule out or confirm a diagnosis of cervical cancer. If cancerous cells are found they can be surgically removed via freezing (cryosurgery), electrosurgery (LEEP) or conventional surgery.
Treatment for other HPV-associated cancers of the head, neck, penis, vulva, throat and mouth include surgery, radiation therapy and chemotherapy.
How can you prevent HPV-associated cancers?
The only guaranteed way is to abstain from all sexual contact. Or you can remain in a mutually exclusive sexual relationship with a confirmed HPV-free individual. Unfortunately, both strategies are not only impractical, they are nearly impossible.
Consistent and correct use of a latex condom during intercourse can protect somewhat, but it won't protect against transmission that can occur without penetration through skin-to-skin or genital-to-mouth contact. Even infected couples in a mutually monogamous relationship can still transmit the virus back and forth to each other.
In June 2006 the US Food and Drug Administration (FDA) approved the first vaccine, Gardasil, to prevent HPV types 16 and 18, that cause 70% of cervical cancer cases, and types 6 and 11, the cause of most genital warts. It does not protect against all high-risk HPV types and does not treat existing HPV infections with types 6, 11,16 and 18.
What are the current recommendations for HPV vaccination?
The Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices recommends that boys and girls 11 and 12 years of age receive a series of 3 doses spaced over a period of 6 months. It may be given starting at age 9. This is to protect them from getting HPV before they become sexually active. Since the vaccine is new, anyone ages 13 through 26 years can "catch up" if they have not yet been vaccinated.
The reason why the vaccine is not recommended for those older than age 26 is because the vaccine is most beneficial to women who haven't yet been exposed to the virus. Furthermore, the research done on the vaccine so far has not shown any significant reduction in HPV-related outcomes for those over the age of 26 years of age.