Leading article: We have a moral imperative to act

There is bad news and good news about the Aids epidemic whose deadly grip is continuing to spread across the globe. The headline fact is that it continues to grow. Some 40 million people are now living with HIV. This year, 12,000 additional individuals have been infected every day. And things are worst among the poorest. Africa increasingly bears the brunt of the epidemic. Three million people died from Aids this year - three quarters of them Africans. That's 5,000 a day - and 1,400 babies were daily born with the disease or were infected by their mothers' milk.

The figures are numbing. Aids is now the leading cause of death among members of parliament, teachers and business leaders in the continent and - a sinister development - African women are now more likely than men to contract the disease. A swathe is being cut through the continent. Average life expectancy there is now just 47 years. Worst of all, there are worrying signs that countries where infection rates were stable, or in decline, are seeing a resurgence of the disease.

But there is good news. There are drugs to treat this. Antiretrovirals (ARVs) are now so good that they produce a "Lazarus" effect - patients at death's door can be back at work within two months. And access to ARVs has jumped dramatically in Africa. The World Health Organisation says there has been a tenfold increase, with more than a million people now on the treatment. And because Africans adhere to drug-taking regimens much better than Americans or Europeans, the success rate is near 90 per cent.

But more is needed than drugs. The other flicker of good news is that the deadly creep of the disease can be stemmed, with the right strategies. Six of the 11 most-heavily affected African countries reported an HIV-decline of 25 per cent or more among young people, between the ages of 15 and 24, in their capital cities. Countries such as Uganda and Senegal have shown that HIV rates can be brought down through prevention. In Uganda, education campaigns - pressing young people to delay the start of sex, increased use of condoms, and fewer sexual partners - cut infection rates from 14 per cent in the 1990s to less than 7 per cent in 2005. HIV among young people is down in Botswana, Burundi, Côte d'Ivoire, Kenya, Malawi, Rwanda, Tanzania and Zimbabwe.

The places where increases have occurred are those where there have been no prevention programmes that focus on those most at risk - young people, women and girls (only 20 per cent of young women worldwide understand how to prevent HIV transmission), sex workers and their clients, men who have sex with men and injecting drug users. Experience in the West teaches the same lesson; in North America and Western Europe, the number of new infections has remained the same because racial and ethnic minorities and migrants have not been targeted - three-quarters of heterosexually acquired HIV infections in western and central Europe are among immigrants, though the main risk factor remains unprotected sex between men.

There are other successful ways of targeting the disease. African governments need to tackle the stigma which persists for those with HIV. They need, by campaigns and by setting an example, to encourage people to get tested - and they need to provide them with healthcare and support if they test positive. Western donors need to understand that no amount of cash for drugs will work if aid promises are not kept that we will invest in improving health systems. In many African communities, there is just not the infrastructure nor the health workers to administer and monitor the treatment. About four million more barefoot doctors and nurses are needed if universal access is to be delivered.

What is needed is more cash. Unaids estimates that $23bn will be required every year by 2010 to provide prevention, treatment and care services for all. At current rates of progress, spending will reach only half that amount. Next year the gap between what has been promised and what will be delivered with be $8.1bn. Donors such as the United States and the UK have upped their giving significantly, but more is needed. The US Congress must resist the temptation to give President Bush a bloody nose by cutting the increased amount he has requested for his Pepfar anti-Aids programme and for the Global Fund to Fight Aids. Other countries need to increase their aid considerably.

We can all do our bit. Project Red, which The Independent supports again today, channels all the money it raises into the Global Fund which has, over the past five years, given a total of $5.6bn in 400 grants to 132 countries to combat the disease. This year, Global Fund-financed programmes have provided antiretroviral treatment to more than 550,000 people living with Aids, tested and counselled 5.7 million people for HIV and provided essential care and support to 560,000 orphans. It has demonstrated itself a highly effective mechanism. And yet despite that it will be $400m short of the money it needs this year.

Funding that gap is a practical as well as a moral imperative. For Aids is, in the words of Kofi Annan, the single greatest reversal in the history of human development. The theme of World Aids Day today is that each of us must declare that "Aids stops with me". So it does. On Aids, silence is death. And so is inaction.