A groundbreaking study of couples led by Professor Eduardo Franco, Director of McGill University's Cancer Epidemiology Unit, in collaboration with a team of colleagues from McGill and Université de Montréal/Centre Hospitalier de l'Université de Montréal (CHUM), found more than half (56 per cent) of young adults in a new sexual relationship were infected with human papillomavirus (HPV). Of those, nearly half (44 per cent) were infected with an HPV type that causes cancer.
Dr. Ann Burchell, the Project Coordinator and a former PhD student and post-doctoral fellow with Dr. Franco at the Cancer Epidemiology Unit, conducted the HITCH Cohort Study (HPV Infection and Transmission in Couples through Heterosexual activity) to determine the prevalence of HPV infections among recently formed couples. This is the first large-scale study of HPV infection among couples early in their sexual relationships when transmission is most likely.
The results, published in the January 2010 issues of Epidemiology and Sexually Transmitted Diseases, also indicate there is a high probability of HPV transmission between partners. When one partner had HPV, the researchers observed that in 42 per cent of couples, the other partner also had the infection. Moreover, the researchers found that the presence of HPV in one partner was the strongest predictor of finding the same HPV type in the other partner. If one partner was infected with HPV, the other partner's chance of also being infected with the same HPV type increased over 50 times.
"These results build on our knowledge that HPV infection is very common among young adults, and underline the importance of prevention programs for HPV-associated diseases such as cervical cancer screening and HPV vaccination," said Dr. Ann Burchell. "Our results also suggest that HPV is an easy virus to get and to transmit. Our estimates of the HPV transmission probability will be of use to other researchers who use modeling to project the public health and economic impact of HPV vaccination strategies."
HITCH Cohort Study participants are young women attending university or college/CEGEP in Montreal, Quebec, and their male partners. New couples are defined as those who have been together for six months or less. Participants fill out questionnaires in which they answer questions about their sexual history and they also provide genital specimens for laboratory testing for the presence of HPV infection. Recruitment for the study is continuing.
"Our study is the first to investigate HPV transmission in a large number of new couples among young adults," says Dr. François Coutlée, a professor at the Université de Montréal Department of Microbiology and Immunology and researcher at the Centre Hospitalier de l'Université de Montréal where the HPV tests were analyzed. "The results suggest that many HPV transmissions occur at the start of new relationships, which reinforces the need for prevention."
HPV is sexually transmitted and causes cervical cancer as well as other cancers, including those of the vulva, vagina, anus, and penis. Although HPV viruses are very common - more than 70 per cent of women and men will have this type of infection at some point - the vast majority of infections are asymptomatic and last no more than one or two years. Fewer than 1 per cent of women who have HPV will get cervical cancer.
The Canadian Institutes for Health Research provided support for this study and for Dr. Franco's research program on HPV and cervical cancer, with supplementary and unconditional funding support by Merck-Frosst Canada Ltd. and Merck & Co. Ltd. Dr. Burchell was supported by a research studentship from the Canadian Cancer Society Research Institute and by a Richard H. Tomlinson doctoral fellowship to McGill University.