A lot of factors have fuelled the spread of HIV in Eastern Europe and Central Asia, mainly official apathy, discrimination and criminalisation of drug addicts.
The six-day World AIDS forum staged a series of workshops and seminars where policymakers and grassroots workers portrayed a regional pandemic growing at murderous pace.
Authoritarian policies, homophobia and a refusal to accept solutions tested elsewhere and proven successful are to blame, many said.
The main vector for spreading the AIDS virus is shared use of syringes among intravenous drug addicts, followed by sexual transmission by these individuals to their partners, Martin Donoghoe, programme manager for HIV/AIDS for the World Health Organisation (WHO) in Europe, told AFP.
Many infected drug users then turn to prostitution to feed their habit, which thus enables HIV to be catapulted into the mainstream, researchers have also found.
"The first intervention would be to give clean needles and syringes to drug injectors. This helps prevent transmission of the virus," said Donoghoe.
"The second is to get the drug injectors into drug dependence treatment," such as substitution therapy with methadone, he said.
Years of experience in Western Europe and other countries have shown that these so-called Harm reduction programmes, when combined, can reduce new infections of HIV by up to half.
But in most of Eastern Europe and Central Asia, the programmes are not implemented -- not for lack of funds, but because political resistance.
"It remains controversial in eastern Europe," explained Donoghoe. In particular, "there are some questions regarding whether you should be giving what is basically a drug to substitute for another drug."
Use of methadone for therapeutic purposes was especially banned in Russia, he said.
Some 1.5 million people in the region were infected with the human immunodeficiency (HIV) in 2008, compared to 900,000 in 2001, according to UNAIDS.
More than two-thirds of them lived in Russia, which combined with Ukraine accounts for more than 90 percent of the region's infections.
According to the UN child protection agency Unicef, more than 80 percent of those infected with HIV in eastern Europe and Central Asia were under 30 years old.
Other marginalised groups were street children, prison inmates, homosexuals and immigrants.
"There hasn't been any nationwide prevention campaign," said Olga Dudina, who works with a Ukrainian NGO.
"More than 60 percent of prisoners don't have any real access to testing or treatment," she noted.
Timur Abdulaev, an advisor on AIDS from Uzbekistan, agreed.
"In certain countries, there is a culture of silence: governments say 'we don't have any homosexuals, any prostitutes'. Denying the problem doesn't help solve it," he said.
The 18th International AIDS Conference, which ends in Vienna on Friday, placed the spotlight on the region's problems as the venue is the gateway to eastern Europe.
But no high-ranking official from the region responded to invitations from the International AIDS Society (IAS), which organised the forum.
IAS President Julio Montaner, a leading figure in AIDS research, singled out South Africa for praise, saying the attendance of its deputy president, Kgalema Motlanthe, showed the HIV-ravaged country no longer denied its own problems.
"On the contrary, the leadership of some Eastern European countries... has shown total indifference to our plea," Montaner said angrily.
"Not being here is actually being heard loud and clear as a sign of being irresponsible to the point of criminal negligence."