The Big Question: Are we making any ground in the fight against Aids, and can the war be won?

Why are we asking this question now?

More than 24,000 scientists, activists, health workers and other experts are in Toronto for the 16th International Aids conference -the biggest ever held. The week-long event will hear about the latest progress in preventing HIV infection and treating Aids, 25 years after the first cases were reported. Many at the conference, including the billionaire philanthropist Bill Gates, who was a keynote speaker yesterday, believe medical science may be on the cusp of a real breakthrough in beating a modern-day plague that has so far killed more than 25 million people and infected 65 million more.

How is the war on Aids going?

Progress is varied. Overall, epidemiologists believe rates of infection peaked in the 1990s and are stabilising - and, in some countries, beginning to decline. The latest report by the Joint United Nations Programme on HIV/Aids (Unaids) estimates that 38.6 million people worldwide are living with HIV. More than 4 million were newly infected last year and 2.8 million died from Aids.

Prevention, testing and treatment services have all improved massively over the past few years. The number of people who undergo HIV tests and counselling has quadrupled since 2001 to 16.5 million. More than 1.3 million people now receive life-prolonging antiretroviral (ARV) therapies compared with just 240,000 five years ago.

Funding has also increased; more than £4bn a year is now spent on researching and treating the disease. But the World Health Organisation's "Three by Five" goal of having 3 million people on ARV treatment by the end of last year was not met - only 20 per cent of those infected are on such therapies.

Is it only Africa that has to worry?

Sub-Saharan Africa remains the epicentre of the epidemic; two-thirds of people infected with HIV live in the region. One in three adults in Swaziland is HIV positive and South Africa, Botswana, Lesotho and Namibia have similarly high rates of prevalence that have shown no clear signs of decline.But it is by no means simply an African problem. More than 8 million people in Asia are infected and two-thirds of them live in one country - India - where less than 10 per cent of patients are on ARV treatment. Prevalence is also increasing in China, Indonesia, Papua New Guinea and Vietnam.

The tipping point in any HIV epidemic is 1 per cent - when more than this proportion of the population is infected, the spread of the virus moves from high-risk marginal groups (such as injecting drug users, sex workers and gay men) and into the wider community.

Burma, the Bahamas, Trinidad and Tobago, Belize and Honduras are among the countries outside Africa with an HIV prevalence of more than 1 per cent. The number of people living with HIV in Eastern Europe and Central Asia has increased twentyfold in less than a decade. Russia now has the biggest Aids epidemic in Europe, with an estimated 1.5 million people infected with HIV and has also reached the "tipping point" of 1 per cent.

In the UK, there were more than 6,000 newly diagnosed cases of HIV last year, more than 3,000 of which were thought to have been acquired through heterosexual sex.

Are some countries better than others at fighting Aids?

Six out of 11 African countries heavily affected by HIV last year reported a decline in prevalence of at least 25 per cent among the key demographic of 15-24 year olds in capital cities. For the first time last year Kenya, Zimbabwe, Burkina Faso and Haiti also began to show signs that infection rates are falling.

One of the biggest success stories has been Uganda, where prevalence has fallen from 15 per cent in the early 1990s to 6.7 per cent in 2005. Uganda adopted an "A-B-C" campaign, which promotes abstinence, followed by encouragement to "be faithful" but also teaches condom use. Lesotho has announced a £7m programme to test its entire population for HIV in an attempt to increase access to treatment and reduce stigma.

What is the focus of scientific research?

Until 10 years ago, there was little doctors could do to help the victims of HIV/Aids. Then along came Haart (highly effective antiretroviral therapy) which revolutionised treatment.

Last month the US Food and Drug Administration approved a new type of ARV that combines three drugs in one pill and is taken just once a day, compared with older style treatments that involve several pills a day and have proven to be hard regimes for patients to follow.

Trials of a vaccine are under way in Thailand and results are expected next year. The first HIV vaccine may be available by 2012, but most experts believe it will take far longer, partly because the HIV virus keeps changing.

One of the most exciting breakthroughs could come from the world of microbicide gels that women apply before sex to kill the HIV virus. British scientists from Imperial College London are at the forefront of the research, with the development of a vaginal gel called Pro 2000 which is being tested on more than 10,000 women in South Africa and Uganda.

Five other gels and creams are also in final-stage trials, and Bill Gates said yesterday that he believed their development could be a "turning point" in the fight against Aids, not least because it gives women a way of protecting themselves.

Recent research has also found that male circumcision reduces a man's risk of acquiring HIV by up to 60 per cent, a success rate which experts say a vaccine should achieve.

What does the future hold?

The solution may lie not in the laboratory but in education and awareness. A fundamental change in cultural attitudes towards sex and women, not just in sub-Saharan Africa but across the world is key.

A report published yesterday by the charity ActionAid showed that girls with secondary level education were more likely to wait before having sex, much more likely to use condoms - and therefore much less likely to become infected with HIV. As Bill Gates told the Toronto conference: "We need to put the power to prevent HIV in the hands of women."

Will Aids ever be eliminated?

Yes...

* The success of countries like Uganda has shown that a combination of treatment and education can have astonishing results

* Preventative measures that focus on women are in the final stages of development and could revolutionise the battle

* If an effective vaccine is ever developed, HIV/Aids could go the way of smallpox and polio before it

No...

* The HIV virus has showed itself to be capable of constantly changing and adapting to evade the drugs thrown at it

* Cultural attitudes and sexual mores are too ingrained to expect that all people will follow the advice and education given to them

* While governments like that of the US continue to preach abstinence over condoms, there is little hope of an Aids-free world