TORONTO, Aug 14, 2006 (AFP) - In an update on the AIDS pandemic, researchers Monday described a disease which was unfolding in myriad ways, advancing in some parts of Africa but held back in others, and which had South Asia and the countries of the former Soviet bloc in its sights.
And, in their presentations at the 16th International AIDS Conference, they also pointed to a potential Achilles heel that one day could expose the murderous pathogen to vaccines, microbicide gel and new treatments.
US epidemiologist Chris Beyrer of the Johns Hopkins Bloomberg School of Public Health said the HIV/AIDS pandemic was "very diverse" in where and how it was spreading.
As a result, a one-size-fits-all strategy for fighting the disease has to be ditched in favour of targeted responses which meet local needs, he stressed.
Beyrer said HIV was spreading fastest in Eastern Europe, Central Asia and the former Soviet Union.
"The epidemics are really being driven by increasing and widespread heroin availability, largely because of the tremendous increase in heroin production in Afghanistan," said Beyrer.
In the case of Ukraine, 68 percent of HIV infections were intravenous drug users who shared infected syringes, and the tally was 20 percent in Russia, he said.
There, as in other countries, governments were failing wretchedly to set up programmes to enable drug addicts to exchange syringes for clean ones and to acquire methadone as a safer substitute for heroin, he said.
Another big worry was the rise of infections among gays and male bisexuals.
"We are seeing an ongoing spread in first-world settings, particularly in the United States, but also emerging epidemics in developing countries," he said, pointing to homophobic stigma and silence that allowed the virus to spread stealthily.
In Africa, said Beyrer, the AIDS picture shows a continent that is even more divided than before.
South of the Sahara, which has 11 percent of the world's population, is home to nearly two-thirds of the 38.6 million people with AIDS or the immunodeficiency virus (HIV) that causes it.
But it is hugely concentrated in the south of the continent. The agency UNAIDS estimates that approximately 40 percent of the world's HIV-positive population lives in southern Africa, and roughly 37 percent of all new infections in 2005 occurred here.
"The southern African epidemic is much more severe than the rest of Africa and it appears to be continuing to expand, while there's evidence in the east, west and the Horn of Africa that the HIV epidemic actually is slowing," said Beyrer.
Beyrer pointed to some deep sources of HIV infection that explained why South Africa and its neighbours were so at risk: labour migration, gender inequality, domestic violence "and probably some biological factors, such as low rates of male circumcision, high rates of herpes simplex virus and low condom use."
Separately, a report by the World Bank sounded a warning for India and the other countries of South Asia.
It described the epidemic there as "severe" but also preventable, provided that awareness campaigns and treatment were shaped according to local needs, focussing on sex workers and their clients, drug users and their sex partners, and gays.
"If we can protect vulnerable groups we can avert an epidemic in South Asia," said David Wilson, a World Bank specialist.
AIDS has killed 25 million people since it first emerged 25 years ago. Last year, it killed 2.8 million people and 4.1 million became infected with HIV.
Scientists at the world AIDS conference, which opened on Sunday and runs for six days, explained their latest work in the quest to devise a vaccine and a vaginal cream, called a microbicide, to thwart infection.
Julie Overbaugh of the Fred Hutchinson Cancer Research Centre, in Seattle, Washington, said evidence was slowly building about genetic vulnerabilities among some people to HIV and about weaknesses within the virus itself.
Put together, they could be HIV's "Achilles heel," she said.
Overbaugh pointed to a sugary coating, called glycosylation, that had been identified among strains of HIV that were especially resistant to attack by antiretroviral drugs.
"The sugars essentially shield the virus protein and block other molecules getting at the virus," she said.
"So one area of interest is to see if we can find antibodies that would bind specifically and get access to those particular viruses by getting through that sugar coat."
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