In the past 10 years, Canadian teenagers have experienced a disturbing rise in sexually transmitted infections, according to public health officials.

From 1997 to 2006, among teens aged 15 to 19, there was an almost 50-per-cent jump in the number of reported chlamydia infections, from a rate of 546 for every 100,000 people to 816. And there was a 100-per-cent increase in gonorrhea cases, from 52 for every 100,000 people to 100.

While the rates of sexually transmitted infections has increased across all age groups - chlamydia, for one, has risen 77 per cent - a number of public health agencies yesterday urged Canadians to step up their education efforts for adolescents and teens.

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"When you look at health policy and health services, preventing STIs is not necessarily high on the agenda," says Linda Capperauld, executive director of the Canadian Federation for Sexual Health, which advocates the use of contraceptives plus condoms among teens.

"It may be that some people are under the impression that if you get an STI, you find it and you get it treated," she says.

While the new rates are troubling, public health officials say they're only part of the picture. "We know that these numbers are an underestimation of the actual proportion," Public Health Agency of Canada analyst Rhonda Kropp says.

This is especially risky when it comes to chlamydia, considered a major cause of pelvic inflammatory disease, ectopic (tubal) pregnancy and infertility, because symptoms can be invisible.

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The Society of Obstetricians and Gynaecologists of Canada yesterday urged educators, parents and health workers to step up their efforts to educate teens about the risk of STIs. The society hopes to steer Canadians to two of its websites, sexualityandu.ca and hpvinfo.ca, for information to share with teenagers.

In an editorial published in the group's Journal of Obstetrics and Gynaecology Canada this month, sexual health expert and University of New Mexico pediatrician Victor Strasburger notes recent Canadian surveys in which a majority of students in grades 10 and 12 felt they couldn't talk to their parents about sex. Instead, they glean their information from TV, film and the Internet, he writes.

"When you look at the surveys, it's very clear youth want to be able to go to their parents," Ms. Capperauld says. "A lot of people who are parents didn't get very good sexual health education themselves."

But the main culprit behind rising STI rates, many experts agree, is simply the unpopularity of condom usage among youth.

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It's confounding since there are other positive signs that "youth in Canada are attempting to take control of their sexual health," Ms. Capperauld says.

Contrary to popular opinion, teens are not initiating sex at an earlier age than previous generations and they have fewer partners than previous generations. They've also embraced oral contraceptives, according to the Canadian Federation for Sexual Health's recent report, Sexual Health in Canada. But in many cases, they're stopping short of adding condoms to the mix.

"Often the kind of information or professional guidance youth are getting is focusing on not becoming pregnant," says Ms. Capperauld, who is a trained social worker.

In some cases, adults are also willfully throwing up obstacles. Ms. Capperauld says she and her colleagues continue to hear stories like that of a young man in a rural area who was asked for identification when he attempted to buy condoms at a pharmacy.

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The federation wants to find out more about those who do use condoms. It uploaded a survey onto its website and on Facebook yesterday to begin collecting data.

"We think if we can find out why they do use them, we might be able to find ways to educate and influence not only young people but health care professionals and teachers to promote those reasons."