A record number of gay men were diagnosed with HIV last year, fuelling concerns that a dangerous complacency has set in about the virus that causes Aids.
Figures from the Health Protection Agency (HPA) show there were 2,356 new diagnoses among the gay community in 2005, bringing the number of gay men in the UK who know they have the virus up to 19,000.
The number of new cases among homosexuals has almost doubled in 20 years. A further 9,000 are estimated to be HIV positive but unaware.Charities said the success of antiretroviral (ARV) treatments was increasing the "infection pool". Increased uptake of testing may also explain part of the rise in new cases.
But there are also fears that younger men believe the virus is treatable and are having unprotected sex.
Will Nutland, head of health promotion at the Terrence Higgins Trust, said: "Young men now are not growing up in the same culture as 15 years ago, when you went into gay clubs and saw people who were decimated by HIV and Aids. You cannot expect younger men to understand what it was like then, particularly because HIV is not considered a death sentence any more." He added: "Someone may have HIV but be on treatment and look healthy and not be disclosing their status, or not be aware."
Because ARV treatment also reduces the infectivity of a person, men who are on the drugs may also believe they have a reduced chance of passing the virus on. There are also concerns that the Government is failing to inform high-risk groups of the dangers.
Mr Nutland said that one third of gay men left school without basic sex education about protecting themselves from infections.
Experts believe HIV sufferers who access the drugs early may now live for up to 30 years before Aids develops. Deaths from Aids have fallen from a peak of 1,469 in 1996 to under 500 a year.
However, the number of new cases of HIV diagnosis has risen from 3,224 in 1985 to 7,450 last year.
In total, more than 60,000 people in the UK have HIV - but a third are unaware.
More than half of all HIV cases were heterosexually-acquired, and 20,000 out of 33,000 are women.The biggest risk groups among heterosexuals are men and women from Africa who acquired their infection there.
Of the 13,400 men in the UK with heterosexually-acquired HIV, 7,500 were African-born, and of 20,200 women, 14,000 are African.