Hidden risks of sex

There are 42 million HIV positive men and women in the world, only 50,000 of whom live in the UK, so it's understandable that World Aids Day focused on countries less fortunate than ours.

But a closer look at the latest British statistics reveals a worrying trend - we are in the grip of an epidemic of sexually transmitted disease (STD) and most of those infected are dangerously unaware they have a problem.

Despite nearly 15 years of safe-sex campaigns, the number of people contacting HIV continues to rise, with heterosexual sex accounting for the lion's share of new cases for the fourth year running, and more than a third of those infected have no idea they are HIV positive. But it's not only HIV that is concerning doctors.

Half of all sexually active women are now infected with the human papilloma virus (HPV - responsible for genital warts and most cases of cancer of the cervix) and as many as one in 10 young men and women carry chlamydia.

The number of new cases of gonorrhoea has doubled to 20,000 a year since 1995, and the number treated for syphilis has risen nearly tenfold. And that's probably just the tip of the iceberg - the real incidence could be five to 10 times higher.

So who is most at risk? Anyone who is sexually active can catch an STD, and the more partners you have had, the higher the risk, which is why most cases occur in the under-25s. Other high-risk groups include anyone who has had a new sexual partner in the previous three months, the recently separated or divorced, and people returning from holidays in Eastern Europe, East Asia and parts of Africa.

But even couples in longstanding relationships can harbour STDs. HIV infection lies dormant for many years, most women with HPV won't ever develop obvious genital warts, and three out of four women and half of all men infected with chlamydia will be symptomless.

There are no routine screening programmes for STDs in the UK although GPs opportunistically test patients who come in for other reasons, including screening all sexually active women under the age of 25 for chlamydia by taking swabs at the same time as routine cervical smears.

There is no such initiative for symptom-free young men, although the Department of Health is evaluating the costs and benefits of a national routine programme.

In the meantime a growing number of patients of all ages are requesting routine STD screening, and I am always happy to oblige. Your local Sexual Health Clinic is the best place to go if you are worried about STDs, and you don't need a referral from your GP.