HPV and Related Cancers in Canada

Human papillomavirus, usually shortened to HPV, is a group of more than 100 related viruses. Many types are spread through skin-to-skin contact, including sexual contact, and health agencies describe it as the most common sexually transmitted infection worldwide. Most infections cause no symptoms and clear on their own.

A small share of infections with certain high-risk types persist for years and can lead to cancer. This link has shaped public health policy in Canada for decades.

Types of HPV

Scientists divide the viruses into low-risk and high-risk types. Low-risk types can cause genital or skin warts. High-risk types, most notably HPV 16 and HPV 18, are associated with abnormal cell changes that may progress slowly into cancer if the infection does not resolve.

Cancers linked to the virus

Cervical cancer is the best-known HPV-related cancer, and nearly all cases are attributed to the virus. HPV is also linked to cancers of the anus, vulva, vagina and penis, as well as cancers at the back of the throat, a group called oropharyngeal cancers. These include tumours of the tonsils and the base of the tongue.

Researchers in several countries, Canada among them, have reported that the share of oropharyngeal cancers linked to HPV has grown over recent decades, even as smoking-related throat cancers have declined. Because the virus is so common, a person can acquire it with few lifetime partners, and the infection can remain dormant for many years before any cancer develops.

Vaccination in Canada

Health Canada has approved HPV vaccines, and the federal national immunization body publishes national guidance on their use. Delivery is a provincial and territorial responsibility, so school-based programs differ in the grades and groups they cover. Provincial programs have expanded over time, and eligibility in many jurisdictions has broadened beyond girls.

Screening

Cervical screening, historically through the Pap test and increasingly through HPV testing, looks for early changes before cancer forms. No comparable routine screening test exists for most other HPV-related cancers, which is one reason prevention through vaccination receives particular attention from public health bodies.