What to know about HPV, the most common STI

Most people will be infected with the virus at some point in life, and a minority will go on to develop cancer

Healthing.ca 4 minute read August 17, 2021

Squamous epithelial cells under microscope. Getty

By: Laura Tennant

“Picture your most recent family reunion,” says Dr. Kimberly Alexander, MD, a gynecologist registered with the Society of Obstetricians and Gynecologists of Canada. “Eighty per cent of the [adults] there have had HPV infections.”

HPV — the shorthand usually used for the human papillomavirus — is the most common sexually transmitted infection. In fact, most people who have sex will get HPV at some point in their lives, though many don’t experience symptoms.

But even when HPV doesn’t cause symptoms right away, it can still cause problems down the line. There are more than 100 strains of HPV. Two strains are linked to genital warts, while several others are linked to cancers. Two in particular — types 16 and 18 — lead to the majority of HPV-associated cancer.

HPV is most often linked to cervical cancer, but it can also cause anal cancer, vaginal cancer, penile cancer, or oral cancer.

There’s no cure for HPV, but genital warts may be treated or removed by a doctor. And HPV infections usually resolve within a few months of infection, says the WHO, with about 90 per cent resolving within two years.

“Most people with HPV will clear the infection on their own,” says Dr. Nancy Durand, MD, an Associate Professor in Obstetrics and Gynecology at the University of Toronto, and a practicing clinician at Sunnybrook Health Sciences Centre.

“Some will not clear the infection and may develop one of the conditions HPV can cause, such as genital warts or pre-cancerous cells. A few will go on to develop cancer of the cervix, vulva, vagina, penis, anus or throat.”

Cervical cancer is treatable when caught early. This is why sexually active women are encouraged to get regular pap tests, also known as pap smears, which can detect the early stages of cervical cancer.

During a pap test, a doctor collects a sample of cells from the cervix. These cells are examined under the microscope for abnormalities associated with cancer and pre-cancer.

“If the pap test is abnormal, the person will be referred to a gynecologist for a more detailed examination of the cervix,” Alexander says. An HPV test can confirm if HPV is involved in the abnormalities.

While cervical cancer remains the main risk associated with HPV, the virus can affect men, too. For most men, the infection usually goes away by itself. But if it does not go away, it may cause genital warts, and some types of cancer, including penile, anal, and oropharyngeal cancer. Men cannot be tested for HPV as there is no approved test.

“HPV-caused cancers of the mouth and throat are four to five times more common in men than women,” Durand says.

The good news is that vaccines are available for HPV. Both Durand and Alexander agree that the best way to stay safe from HPV is prevention with vaccination. Most of the vaccines available today work against multiple strains of HPV, including the ones responsible for genital warts and most cases of cancer.

“The current HPV vaccine protects against nine types of HPV which are responsible for 90 per cent of strains that cause genital warts and 90 per cent of strains that cause cancer,” Durand says.

In Canada, both female and male students receive the HPV vaccine in school. HPV vaccination varies from province to province, but generally it’s given in early adolescence – somewhere from grades 4 to 9, with most provinces giving the immunizations in grades 6 and 7.

“All Canadian kids should get the vaccine in school, as NACI recommends HPV vaccination for everyone under age 26,” Alexander says. “It should also be considered for sexually active people of all ages,” she continues.

According to ImmunizeBC, the vaccines prevent nearly 100 per cent of cervical cancer caused by the nine HPV types covered by the vaccine. It also prevents nearly 78 per cent of anal cancers in men and 90 to 100 per cent of genital warts in men and women.

Although the vaccine should ideally be given before a person becomes sexually active, it appears to be safe and effective even in those who have been infected with HPV.

Most people get infected with HPV within the first 5 to 10 years of sexual experience, but according to the NACI, a second peak is observed in women over age 45.

“It is not uncommon to be diagnosed with HPV over age 50,” says Durand. “This could result from a new HPV exposure. It can also result from an HPV infection acquired at a young age which had become dormant, but which reactivated because the immune system weakens as we age,” she explains.

As more and more Canadian kids get vaccinated against the virus, the hope is that HPV-associated cancers will reduce in prevalence.

Adults can consider speaking to their doctors about HPV vaccination, and women should continue to get regular pap tests. Anyone with symptoms should speak to a healthcare provider.