There is particular concern about the rapid spread of HIV and genital herpes and a warning that people must take precautions.

Doctors meeting at a conference in Budapest, Hungary, were told that safer sex messages were doing little to check the spread of serious diseases.

The problem is reaching epidemic proportions in some eastern European countries.

More than 100 million people worldwide were infected with the virus that causes genital herpes and over 30 million were thought to be carrying HIV.

In the US, 12 million new STD infections were diagnosed each year. In Britain, there were more than 27,500 cases of herpes in 1996.

Incurable disease

Worldwide publicity campaigns needed

Professor Richard Whitley, from the International Herpes Management Forum (IHMF), which organised the meeting, said: "One of the most worrying public health problems today is the dramatic rise in the number of people infected with genital herpes.

"This is of particular concern as genital herpes is an incurable disease and has been associated with an increased risk of acquiring HIV."

Genital herpes is a close relative of the virus that produces cold sores around the mouth.

The virus lies dormant in nerve cells for long periods, occasionally emerging to cause painful blisters on the genitals.

Oral sex danger

Although two different forms of the virus, Herpes simplex, cause cold sores and genital infection, they can be interchangeable. It is possible to contract genital herpes from a cold sore through oral sex.

Sixty per cent of people with genital herpes have signs or symptoms of the disease, but are undiagnosed. Research has indicated that only a quarter of those infected with herpes are aware they are carrying the virus.

A genital herpes sufferer is eight times more vulnerable to the HIV virus than average as HIV can replicate in herpes lesions.