THE burning sensation in her groin hurt so much that the 19-year-old girl couldn't sleep.

Walking was also painful.

The girl had contracted herpes, resulting in many small ulcers in the vulva area from having unprotected sex with her boyfriend. The recurrent outbreaks from the incurable disease made it hard for her to continue her part-time job as a shop assistant as she had to be on her feet most of the time.

Now she has to take anti-viral drugs whenever she feels she is about to get an outbreak. She also has to take care that she does not pass on the sexually transmitted infection (STI) to future partners.

Dr Madeleine Chew, 38, a general practitioner of 14 years, saw the girl about a year ago. "She was very disturbed by how the condition affected her lifestyle, work and studies," said Dr Chew, "as she was in such severe pain then."

Teenagers with STIs appear to be on the rise. In a written reply to a question by MP Ellen Lee in Parliament, the Ministry of Health noted a more than 50 per cent jump between 2000 and 2008 in the number of STI cases among those under age 20.

The figures, released by the DSC Clinic in Kelantan Lane, exclude HIV. Two-thirds of those under 20 who had STIs were women.

Ms Lee, 52, MP for Sembawang GRC, was concerned over media reports in the past year that more teenagers were having sex. Two years ago, the parents of a pregnant girl who was under 14 had sought legal advice from Ms Lee, a lawyer.

Under the law, a person who has sex with a minor under 14 can be jailed up to 20 years with a fine or caning.

Ms Lee said: "There were reports of more young people having sex, more one-night stands, so I wanted to see if rates of STIs have also increased."

Next: A "wake-up call" for parents