Most people infected with human papillomavirus (HPV), the most common sexually transmitted infection (STI), are unaware that they have it, making it easy to spread.

When the Food and Drug Administration first approved a vaccine for the human papillomavirus (HPV) in 2006, most people knew little about the virus or its link to certain cancers. But according to the American Cancer Society, 80% of people will get HPV in their lifetime.

What exactly is HPV?

HPV is the name for a class of viruses that includes more than 100 different strains — of which more than 30 are sexually transmitted. The CDC estimates that approximately 48 million people were infected with HPV in 2018, many of whom are in their teens and early 20s. About 13 million Americans contracted new HPV infections that same year.

Infection usually goes away without causing any health issues. But each year, 35,000 men and women will develop HPV cancer in the United States.

As an STI, HPV is transmitted through vaginal, anal or oral sex, regardless of whether the person passing on the infection experiences any signs or symptoms. As a result, HPV can cause cancer of the anus, oropharynx (back of the throat, tonsils and base of the tongue), penis, vagina and vulva. HPV can also cause precancerous genital lesions and warts.

How is HPV prevented and will it go away on it's own?

There is no cure for HPV, but there is a vaccine — Gardasil 9, which is approved for those 9 to 26 years of age. It helps prevent six types of cancer, including cervical cancer.

Although Gardasil 9 does not protect against all HPV strains, it protects against cancers caused by HPV types 16, 18, 31, 33, 45, 52 and 58; and genital warts caused by types 6 and 11.

Ideally, children ages 11 and 12 should be vaccinated for the virus, because the vaccine's cancer-prevention attributes decrease as the age at which vaccination occurs increases. So it is best to get the vaccine before age 13.

In children 9 to 15, the vaccine is given in two injections, six months apart. From ages 15 to 26, the vaccine is given in three doses, with the second one given one to two months after the first dose, and the third dose given six months after the initial dose.

Even if a person is sexually active and has contracted one of the strains of the virus, the vaccine will still protect against other strains. Early vaccination gives children the opportunity to build up antibodies to the nine strains found in the vaccine, since younger children have an elevated immune response to the vaccine and will develop a higher number of antibodies before they encounter the virus.

Are there obvious signs or symptoms of HPV?

Unfortunately, HPV is a hidden disease. It lives in the skin or mucous membranes, and except for genital or anal warts caused by some strains, there are no physical symptoms.

Men and women can contract HPV through sexual intercourse or genital contact. Condom use does decrease the rate of transmission, but it doesn't eliminate it, meaning that not even a condom can fully protect against transmitting the virus. Abstinence and monogamy are the best defenses against contracting the virus.

HPV cancers are more common in women than men, with 3 out of 5 cases impacting women each year. Vaccinating males also would aid in halting the spread of HPV to females.

What is the risk for developing cervical cancer from an HPV infection?

There are certain protocols in place to test for HPV infection if a woman's Pap test shows cellular abnormalities. About 90% of women exposed to the virus will fight the infection on their own. The rest will develop a persistent infection that will create abnormalities in the cervical cells. Eventually, if left untreated, precancerous abnormalities, known as dysplasia, can develop.

Not all women with precancerous changes to the cervix will develop cervical cancer. Sometimes it will go away without treatment. According to one study, more than 99% of cervical cancer specimens showed evidence of HPV infection. However, HPV infection is not the sole cause of cervical cancer. Other factors, such as smoking and a family history of cervical cancer, play a role in determining if a woman will get cervical dysplasia and/or cancer.

What about Pap tests and HPV?

It's better to be safe than sorry, and women shouldn't forgo annual Pap tests, even if they have been vaccinated against HPV — since Gardasil does not inoculate against all HPV strains that lead to cervical cancer.

The Pap test is designed to detect abnormal and precancerous cells before they become cancerous. Cervical cancer, which develops in the lining of the cervix, takes many years to develop from the initial HPV infection. Annual tests provide multiple opportunities for detecting cervical changes. If caught early, cervical dysplasia and cervical cancer can be treated easily.