There is perhaps no starker divide between rich and poor than that of public health. The rich are living longer and more healthily than ever, while the poor are increasingly falling victim to Aids, malaria, tuberculosis and other emerging and re-emerging diseases. The situation is intolerable, yet the world has failed to take the appropriate steps.

Talk alone will not solve the problems. Money, political will, wise stewardship by the pharmaceutical companies and good science from the world's experts will all be needed.

The first step is to realise that the public health crisis in the poor countries, especially in Africa, is inter-national public enemy number one. Without progress on Aids and the other diseases, economic development itself will be blocked in much of the world.

Second, it must be recognised that poor countries need financial help to fight disease. The poorest countries have annual incomes of just $250 a person. Even public health spending of 5 per cent of gross national product, more than most impoverished countries can achieve, amounts to only $12.50 a person a year - grossly insufficient to tackle the multiple health crises.

Africa would probably need between $10bn and $20bn a year from inter- national donors for disease control but it receives less than $1bn.

Third, pharmaceutical companies should make their miracle drugs for Aids and other killer diseases available at production cost to the poorest countries. In rich countries, the drugs are sold at far above production cost. Price competition is limited by the patents held on the new drugs. This system spurs innovation but it prices the drugs out of the reach of the poorest countries.

The drug companies have recently signalled a willingness to sell their life-saving drugs at a small mark-up over production cost to international donor agencies as long as intellectual property rights are respected; the drugs are properly used; and they are not reimported into the developed countries' markets.

Fourth, any international donor efforts should be based on fundamental precepts of scientific merit, transparency and independent review and evaluation. Many donor projects get a bad name because they are poorly designed, lack the necessary scientific basis and are not subjected to a scientific peer review that can detect errors in design or implementation.

These four basic points can guide us to workable mechanisms for a large-scale assault against the killer diseases in impoverished regions. Take Aids. There are an estimated 24m Africans infected with HIV, of which about 4m-6m have advanced Aids. UNAIDS, the joint United Nations programme on HIV/Aids, estimates that about $3bn will be needed for prevention and community support, focused on programmes to support safe sex; the use of anti-retroviral drugs to block transmission from mother to child at birth; and support for millions of orphans.

For those already suffering from Aids, special combinations of anti-retroviral drugs can prolong life and dramatically reduce the burden of the disease. Parents with Aids can thereby stay in the workforce and children are spared the tragedy of becoming orphaned. Yet the drugs have been too expensive for poor African governments or families to buy and donors and drug companies have not yet devised ways to get the drugs to the poor who need them.

Moreover, unless treatment is available, prevention programmes will not work. Victims of Aids will not come forward.

To treat victims, however, will require donor funds combined with the leadership of the pharmaceutical industry. Drug companies sell their anti-retroviral drugs in developed countries for about $10,000 a year, though production costs are about $500 per year. The drug companies have no customers for their products in Africa at these high prices and they would lose nothing by offering to sell them to the donor agencies at cost. The agencies would then make them available for free to the poorest countries.

Several companies have signalled their willingness to pursue this step but donor countries have not yet stepped forward to close the deal.

We also need to know more about the best protocols for treating Aids in the poorest countries. The World Health Organisation and UNAIDS should co-ordinate this massive effort, drawing on the world's scientific community.

I estimate that the cost of the overall Aids effort would be about $5bn during the next couple of years and would rise to perhaps $10bn as the coverage of treatment was expanded.

This should be part of a co-ordinated disease control effort for Africa of $10bn -$20bn a year. But with 1bn rich people in the developed countries, this would amount to only $10-$20 from each - an irresistible bargain to save millions of lives a year.

The writer is director of the Centre for International Development at Harvard University Copyright Financial Times Limited 2001. All Rights Reserved.