Q: How many teenagers are contracting sexually transmitted infections (STIs)? A: Since 1995 there has been a dramatic rise in the diagnosis of acute STIs such as genital chlamydia, gonorrhoea, syphilis and genital warts. Chlamydia cases increased by more than 200 per cent between 1995 and 2004, gonorrhoea cases by more than 100 per cent and syphilis, which only affects a small number...