Rates of sexually transmitted infections in Canada have increased so much from 1997 to 2004 that experts are calling the phenomenon a "hidden epidemic" and demanding a national strategy.

According to the Society of Obstetricians and Gynecologists, these rates have surged, despite an ongoing barrage of publicity about safe sex.

• The rate of chlamydia rose by 70 per cent to almost 30,000 cases in 2004. People aged 15 to 24 mostly had the infection.
• Gonorrhea infections went up by 80 per cent to 4,013 cases in 2004. Men aged 20 to 29 had the highest rate of infection. Among women, those aged 15 to 24 had the highest number of cases of gonorrhea.
• Syphilis infections rose by a whopping 908 per cent to 598 cases in 2004. Men mainly over the age of 30 had syphilis, with a significant proportion of its transmission occurring between homosexuals.

The SOGC obtained their data from Canada's Public Health Agency, which tracks all reported cases of sexually transmitted infections in Canada.

Doctors believe the rate of infections is increasing because young people are engaging in more unprotected sex. They also have the misconception that oral sex is safe, said SOGC's executive director, Dr. Vyta Senikas.

"Unlike penetrative sex, oral sex is not considered to be a high risk activity," Dr. Senikas said. "I think what teens need to especially realize is that even with oral sex, an individual can become infected.

"It's also an issue of an asymptomatic disease where you don't think you have a problem."

Speaking on Canada AM on Friday, Senikas said that the ease of travel causes concerns that "these numbers may continue to spiral out of control."

Chlamydia, Canada's most prevalent bacterial STI, often doesn't show any symptoms and is found mostly in women. The provinces with larger populations (British Columbia, Ontario and Quebec) saw the greatest rise in the rate of infection.

Vancouver had a large outbreak of syphilis from 1998 to 2001, which accounts for the increase in its rate. But a high number of outbreaks in Toronto and Montreal also helped fuel the increase.

The SOGC thinks the rate of human papillomavirus (HPV) is increasing, but couldn't get any statistics on it because the disease doesn't need to be reported. The genital warts-causing virus can also develop into cervical cancer, which kills 400 Canadian women a year.

By comparison, AIDS only kills 10 women a year in Canada.

According to medical officials in Edmonton, the STI infection rates in Alberta are even higher than the national average. STIs counted for 62 per cent of all reported diseases in Alberta in 2004. That rate was just 37 per cent in 2000.

Dr. Ameeta Singh, a clinical professor at the University of Alberta, said more than half of Alberta's gonorrhea cases are found in people under 24, two thirds are found in men, and one quarter in Aboriginals.

Doctors say many cases of sexually transmitted infections go unreported, so the actual number of cases in Canada could be higher.

They recommend sexually active people have regular STI tests and use protection, even when having oral sex.

However, diseases such as HPV and herpes can still be transmitted by skin-to-skin contact of the genital area.

"I think what's important are regular check-ups, freestanding clinics within the universities, well-placed in the downtowns of cities so that there's easy access. Therefore, they can find out their infection status," Dr. Senikas said on CTV's Newsnet.

Canada has a lower rate of STIs, though, when compared with other countries.

"We do have lower rates than the United States. We're far better than Africa and Eastern European countries," Dr.Senikas said.

"What is noted, however, is that these diseases are climbing in all of the countries I have mentioned. So certainly overall for the number of cases we're doing well. But we were doing a lot better seven years ago. What we would like to do is see that downward trend again."

Transmission of STIs

• Exchanging bodily fluids is the most common way to pass on an infection
• Skin-to-skin contact is another way of transmitting some infections. Condoms may not provide full protection
• Pregnant, infected women can unknowingly pass on some infections to their babies during pregnancy and at birth

With files from CTV's Avis Favaro