The UN's global fund for HIV/Aids, TB and Malaria has $1.5bn to spend. But does prevention or treatment have the greater claim? An opinion piece from the UK newspaper, The Guardian.

Early next year, a group of people - exactly who they will be is still being fought out - will decide how to distribute the $1.5bn so far collected in the name of UN Secretary General Kofi Annan's global fund for HIV/Aids, TB and malaria.

When the fund was launched, in the wake of the public uproar at the spectacle of 39 pharmaceutical giants suing the South African government to prevent it importing cheap medicines, Aids activists were ecstatic. There was a general assumption the fund would buy the antiretroviral drugs (ARVs) that keep people with HIV alive in the west and without which HIV in Africa is a death sentence.

Since then, expectations, along with the contributions from rich nations to the fund, have slumped. Kofi Annan said that $10bn a year was needed. In around nine months $1.5bn has been raised. And the word from donor government quarters is that Aids drugs are definitely not the priority.

Clare Short, the UK's international development secretary, is one of the most influential world leaders in this area. Privately, she does not believe the fund should ever have been launched - her view is that existing bilateral aid programmes can best tackle the problem. But since it exists, she is clear that it must focus equally on three diseases, not one - TB and malaria as well as HIV/Aids. And she firmly believes that the best way to tackle HIV/Aids is through prevention. She wants to see the fund paying for condoms and microbicides, not expensive drugs.

In many ways, her position is logical. Most of the world's 40m people with HIV/Aids do not live in the rich west. It is not conceivable that the fund could raise enough to pay for drugs for all, even at the rock-bottom price of $300 a patient a year which the generic companies are asking for their copycat drugs (the patented versions cost $10,000 a year).

There is no cure for Aids, the argument runs, so the best bet is to stop people developing it. The HIV virus, which causes Aids, is now spread mostly through heterosexual sex, which can be prevented by the use of a condom. If people understand this and act on it, the epidemic can be halted.

But, as the latest figures show, prevention does not appear to be working. Undoubtedly more money spent on education and condoms would help but the primary obstacle appears to be cultural. Of the 5m infected with HIV in 2001, 3.5m live in sub-Saharan Africa which, by and large, is constituted of patriarchal societies where women have little control over their sexuality. The high incidence of rape, frequently exacerbated by war; polygamy; the cultural pressure on women to bear children early and often; their relative powerlessness in relation to men which makes it difficult for them to insist on condoms - all conspire to allow the virus to run unchecked.

Cultural change, the empowerment of women to say no, is the idealistic answer, but it takes decades, if not centuries. Some 3m people are dying a year, leaving orphans in the streets, uneducated, unprotected, unfed and heading for a life of crime if not one day anger and terrorism. There is an urgent humanitarian need to stop the deaths and to change attitudes, and there are those who say that offering treatment will do it.

Most of the 40m people living with HIV do not know they carry the virus. The stigma of Aids, coupled with the knowledge that it is a death sentence means most would rather not know. NGOs such as Médecins sans Frontières argue that treatment produces a change in behaviour. If people know that they will have access to drugs if they are infected, they are much more likely to come forward for testing. Pre- and post-test counselling provides the first steps towards changing behaviour.

Another compelling argument is economic: the drugs can, hopefully, provide another five to 10 years of healthy life: HIV positive parents can nurture children to adulthood in that time; employees can remain economically active. Teachers, health workers and other key professionals will be able to stay in their posts longer. And hospitals will not be overwhelmed by repeated admissions for opportunistic infections by HIV positive patients.

And then there are the human rights of the 40m already infected. How can it be ethical to write them off?

The biggest obstacle - apart from funds - to treating people with HIV/Aids in poor countries is the lack of health care facilities. Many cities have more than adequate hospitals where they could start using ARVs tomorrow, yet in some rural areas there is barely a basic clinic, a doctor and a nurse. But a project in Haiti started by Harvard scientists found it was possible to disseminate ARVs in the same way as TB drugs - a low key approach in which community health workers make an assessment of people's need for treatment without complicated blood tests, counsel them and ensure they take their drugs within the necessary time frame.

Gradually the obstacles to ARVs for Africa's poor are being surmounted, but it will take courage and imagination for the global fund to hand out money for poor countries to spend on drugs. Politics is a further obstacle. The US, Britain and European nations are vulnerable to pressure from the pharmaceutical lobby. Following the prevention route bypasses clashes of interests. Most donor country politicians would rather leave the drug companies to offer discount deals to those countries that have enough money to treat a small minority of sufferers - as they are now doing.

But the genie will not go back in the bottle. Now that the drug companies are offering Aids drugs at discount, albeit too expensive, prices, there will be demands from activists and unrest from those with HIV. The task for those who will sit on the global fund panel, judging the bids for the money, is going to be tough.