Human papillomavirus (HPV) infections are the most common sexually transmitted infection in the United States, according to the Centers for Disease Control and Prevention (CDC). Nearly 80 million people, around one in four, are currently infected with HPV in the United States, and 14 million new people become infected each year.
Most sexually active men and women will be infected at some point in their lives, according to the World Health Organization (WHO). A 2017 study published in the Journal of the American Medical Association (JAMA) Oncology found that nearly half of American men under the age of 60 have an HPV infection.
There are more than 100 varieties of human papillomavirus, and many types do not cause problems. Low-risk varieties usually clear up without any intervention, and 90 percent clear up within two years. However, at least 13 types of HPV are high-risk, according to the WHO, and these infections can persist and progress to cancer. Researchers from the CDC that found 23 percent of the participants in their study, published in early 2017, were infected with a high-risk strain of genital HPV.
HPV is contracted through skin-to-skin contact, most commonly sexual contact, such as vaginal, anal or oral sex. All genders and sexual orientations can be infected by HPV. "Both men and women can acquire the infection, and since HPV is the most common sexually transmitted infection in the U.S. and in the world, almost all females and males will be infected with at least one type of HPV at some point in their lives,"Dr. Barbara Pahud, associate director of the vaccine unit at Children's Mercy Hospital, told Live Science.
While most people don't have symptoms from HPV, some will develop warts, or papillomas. This symptom varies, depending on the type of virus, and can include genital warts, plantar warts and common warts.
More than 40 types of HPV affect the genitals, according to the Mayo Clinic. HPV 6 and HPV 11 cause 90 percent of all genital warts, according to the U.S. Department of Health and Human Services. Most people will not have any symptoms because the body's immune system will fight off HPV before it causes any harm.
While HPV, for the most part has no apparent symptoms, it may cause various conditions that can create various symptoms. According to the CDC, HPV infection can cause cervical, vaginal and vulvar cancers in women and penile cancer in men. Anal cancer, cancer of the back of the throat (oropharynx) and genital warts can also be caused by HPV in both men and women.
HPV is particularly linked with cervical cancer. In fact, it is the only known cause of cervical cancer in women. According to WHO, HPV types 16 and 18 cause 70 percent of precancerous cervical lesions and cervical cancers.
HPV "typically invades a specific area of the cervix referred to as the transitional zone," said Dr. Eric M. Genden, a professor and chairman of otolaryngology-head and neck surgery at the Icahn School of Medicine at Mount Sinai. "This is an area of high cellular turnover. While the virus integrates into the patient's DNA, the virus typically runs a course of brief infection and then passes. In select few, the virus may persist and result in chronic infection. It those who develop a chronic infection, carcinoma may develop."
The virus affects genders differently. Typically, Genden explained further, women develop a robust immune response to the HPV infection and therefore, fewer women develop viral-related infections. Men, in contrast to women, do not always mount a strong immune response to the infection.
Diagnosis of HPV is usually made after a pap smear. "Anal pap-smear testing can be done for those men who are high risk or have anal sex," said Dr. Sherry Ross, a women's health expert in Santa Monica, California. "In women, HPV can be easily found during a cervical pap-smear screening test. Finding HPV in women is regularly found, compared to finding HPV in men. Women are more likely to get annual gynecologic exams, including cervical screening for HPV. Men do not have regular pelvic/genital examinations making HPV even less likely to be found."
Using protection can lower the risk of transmission during sex. Protection, such as condoms and dams, should be used during any skin-to-skin sexual contact, though it isn't fool-proof.
The HPV vaccine is the best way to prevent HPV. The CDC recommends that preteen boys and girls receive the HPV vaccine at age 11 or 12 so they are protected before the potential of being exposed to the virus. Also, when the vaccine is given to preteens, it produces a more robust immune response.
The HPV vaccine can be administered to women through age 26, and to men through age 21. The CDC recommends, though, that gay men and men with compromised immune systems (including HIV) get the HPV vaccine up to 26.
HPV vaccines are also the favored for the prevention of cervical cancer. A poll of 1,952 U.S. doctors by SERMO, a social media network for doctors, found that 55 percent polled favored state mandates for HPV vaccination. In addition, 92 percent of doctors confirmed that they would vaccinate their own children, despite recent controversy over the safety of the HPV vaccine. The HPV-9 vaccine can prevent around 80 percent of the viruses that cause cervical cancer.
A 2017 report published by JAMA found that the HPV vaccine may even help with skin cancer. This trial was only on two subjects, though, and a much wider group of people need to be tested to confirm the findings.
Side effects of the vaccine, when they do occur, are typically very mild. They include pain, redness, or swelling in the arm where the shot was given, fever, headache, feeling tired or muscle or joint pain, said Genden.
"With all vaccines, it hurts to get a shot in the arm, but that passes," said Pahud. "Teens also may faint after vaccination, but not due to the HPV vaccine itself, but the injection procedure. These findings are similar to the safety reviews of the other two recommended teen-vaccines, meningococcal vaccines and tetanus booster vaccines."