One great challenge facing humanity is reducing the huge gaps in income and wealth between the world's haves and have nots. Dr Gro Bruntland, the head of the World Health Organisation (WHO), has taken up the challenge. She points to the desperate health conditions of the world's poor as one of the greatest barriers to economic development.

Earlier this year, Dr Bruntland appointed a new global Commission on Macroeconomics and Health (CMH), and honoured me by appointing me as its chairman. The commission's task is enormous, but easily described: to help put global public health at the centre of a new strategy of global economic development. It will meet in various parts of the world in the coming two years, and issue its report and recommendations at the end of 2001.

Market reforms alone cannot lift a population from poverty if people are simultaneously struggling with epidemics. Populations battling with disease lack the energy, productivity, or means to invest in their own future. Studies show that when life expectancy is low, so too are many kinds of investments in the future, such as school attendance and personal saving.

Throughout modern history, improvements in public health have speeded economic development. It was Britain's rising agricultural productivity in the 18th century, for example, which helped to raise nutrition levels and reduce the burden of infectious diseases, that helped to initiate the Industrial Revolution. Similarly, eradication of malaria in Spain, Italy, and Greece in the late 1940s helped bring a boom in tourism and foreign investment to these countries in the 1950s and 1960s. That boom enabled Southern Europe to begin to narrow the large gap in income with the richer countries of northern Europe.

Health conditions in many of the world's poorest countries are shockingly bad, and in some cases getting worse. Approximately one-third of children in the poorest countries are malnourished, and at risk of greater incidence of infectious disease and learning disorders.

Life expectancy is little more than 50 years (compared with around 77 years in the rich countries). Millions of poor people every year die of disease.

Ironically, many deaths could be prevented by existing vaccines, but the populations are often too poor to have access to even basic public health. Even in many middle-income and higher-income countries, there have been surges of new and re-emerging infectious diseases, as a result of increased global travel, the opening of new regions to settlement, and the overuse of antibiotics with a resulting spread of disease-resistant parasites. The commission will address these desperate conditions by mobilising evidence showing:

how poor health contributes directly to failed economic development;

working with professionals at the World Health Organisation, UNICEF, the World Bank, the Gates Foundation, and other organisations, to identify public health interventions, such as greater vaccine coverage, that have a very high economic rate of return as well as a high health benefit;

working with the pharmaceutical sector and non-governmental organisations to find creative new ways to get essential medicines to the poorest peoples;

helping to devise new ways to redirect global research and development efforts to unsolved problems, such as an effective vaccine for AIDS, malaria, tuberculosis, and dysentery;

exploring ways to increase overall public spending on vital health needs, by mobilising more international aid, by expanding the depth of debt relief for highly indebted poor countries, and by finding ways that poor countries can increase their own financial efforts.

One of the crucial purposes of the Commission is to help give voice to the health needs of the poorest of the poor.

It will be seeking inputs in advice and research from all parts of the world, and will provide a record of its evidence gathering and deliberations on the Internet. At a time when global science is more dynamic than ever; when the richest countries are experiencing a boom in wealth unrivaled in history, the world yearns for more effective approaches to the struggle against poverty. The WHO is taking its place at the centre of that effort. Jeffrey D. Sachs is Galen L. Stone Professor of Economics, and Director of the Centre for In- ternational Development, Harvard University.