Climate change is the latest threat to the world's growing HIV epidemic, say Australian experts who warn of the "grim" outlook in the fight against the infectious disease.

A leading professor of health and human rights, Daniel Tarantola, has cautioned that global warming will indirectly make citizens of developing countries even more vulnerable to death and severe ill health from HIV/AIDS.

"It was clear soon after the emergence of the HIV epidemic that discrimination, gender inequality and lack of access to essential services have made some populations more vulnerable than others," said Prof Tarantola, of the University of NSW.

Those problems had not gone away, he said, and extra threats were lurking on the horizon "as the global economic situation deteriorates, food scarcity worsens and climate change begins to affect those who were already dependent on survival economies".

"Climate change will trigger a chain of events which is likely to increase the stress on society and result in higher vulnerability to diseases including HIV," said Prof Tarantola, due to address an HIV forum in Sydney.

Prominent HIV scientist Professor David Cooper, director of the National Centre in HIV Epidemiology and Clinical Research, agreed environmental change would have a negative impact on HIV sufferers.

"Climate change will lead to food scarcity and poorer nutrition, putting people with perilous immune systems at more risk of dying of HIV, as well as contracting and transmitting new and unusual infections," Prof Cooper said.

"And this would effect Australia too, because these infections could potentially spread. Just look at the horror that SARS and avian flu have caused."

The specialist said the HIV landscape was grim, with 16,000 new infections worldwide each day and the failure of research to produce a much-needed cure or vaccine.

He echoed the deep pessimism of 35 top British and US scientists who predicted this week that a vaccine would be at least 10 years and maybe even 20 years away.

"It's a pretty grim situation," Prof Cooper said.

"I don't think we have any idea of how to harness a vaccine for this and we need a strong basic science breakthrough to get anywhere with it."

He said it was important to strengthen preventative measures proven to work, like condoms and circumcision, and continue to investigate other more hopeful avenues, like microbicide sex gels and anti-viral drugs to block infection.