At a time when President Bush has lavished billions of dollars in tax cuts on the richest Americans, his trip to Africa presents him with the perfect opportunity to call on them to take some responsibility for the dire state of the world's poorest citizens. According to a recent report from the Internal Revenue Service, some 400 super-rich Americans had an average income of nearly $174 million each, or a combined income of $69 billion, in 2000. Incredibly, that's more than the combined incomes of the 166 million people living in four of the countries that the president is visiting this week: Nigeria, Senegal, Uganda and Botswana. America's richest individuals could actually change the course of Africa's history, and the president -- who has stressed the importance of personal responsibility -- should urge them to do so.

If President Bush gets beyond the typical rhetoric concerning the plight of Africans, he'll discover that poverty throughout the continent is a matter of life and death -- indeed, mainly death. While the average life expectancy in the United States is now 77 years, it is less than 50 years in most of Africa, and less than 40 years in some of the AIDS-ravaged countries. Until the pandemics of AIDS, tuberculosis, malaria and other killer diseases are brought under control in Africa, economic development and political stability will remain crippled. A breakthrough on disease control, conversely, would help to unleash a virtuous circle of rising productivity, better education, lower fertility rates -- and then lead to further increases in health and prosperity.

Yet Africa's poverty makes this an unbeatable problem without more help from the United States and other wealthy countries. In the United States, annual public spending on health care averages about $2,000 per person, according to the World Health Organization. In Africa, public health spending is around $10 per person per year -- not enough to keep the population alive. Countries throughout Africa are desperately trying to do more, but simply can't afford to when their citizens' incomes average less than $1 per day, and when their struggling governments must repay foreign debts to rich nations instead of tending to their sick and dying.

Two years ago the World Health Organization's Commission on Macroeconomics and Health, which I headed, made a stunning finding: If rich countries contributed a total of around $25 billion per year, the increased investments in disease prevention and treatment could prevent around eight million deaths each year in poor countries throughout the world. The United States' share would be around $8 billion, given the size of its economy in relation to other donors. Most of this money is needed in Africa, where the countries are among the poorest and the disease burden is the highest.

Projected spending by the United States on global health in the fiscal year 2004, even with the president's new AIDS initiative, is roughly $2 billion, or one-fourth of what's needed from us. More money could, among other things, keep AIDS patients alive through antiretroviral therapy, help mothers survive the complications of childbirth and prevent hundreds of thousands of children from dying from malaria and vaccine-preventable diseases.

Here's where America's richest 400 could change history. In 1995, the top 400 income earners paid almost 30 percent of their incomes in taxes. After the Bush tax cuts and other factors, the proportion will be less than 18 percent. Suppose the super-rich applied their tax savings toward Africa's survival. That extra 10 percent of income -- which translates to nearly $7 billion based on the incomes in 2000 -- would provide a huge chunk of the $8 billion that the United States should contribute to the global health care effort. This money could readily and reliably be given to the Global Fund to Fight AIDS, Tuberculosis and Malaria, which could then put it to spectacular use in saving those eight million lives each year. For individuals who already have all the earthly possessions that can possibly be amassed, could there be a better way to give meaning to vast wealth?

The notion that the super-rich might voluntarily rise to the occasion is not preposterous, especially if President Bush encouraged them to do so. Bill Gates has brilliantly blazed the way with a donation of more than $20 billion directed mainly at international public health. And many of the super-rich opposed the recent tax cuts, saying the needs of the poor were too great.

Of course, it's strange to rely on only the goodwill of a few hundred super-rich people to save the lives of millions of the poor. All Americans need to share responsibility for such an effort, not only for humanitarian reasons, but also for practical public health reasons. Yet given the huge tax cuts that have gone to the wealthiest Americans, the moral and practical obligations facing them are greater than ever.

Our world is dangerously out of kilter when a few hundred people in the United States command more income than 166 million people in Africa -- with millions of the poor dying each year as a result of their impoverishment. Perhaps most remarkable of all is that such bald facts are rarely noticed in this country. President Bush's trip to Africa should open our eyes to these realities, as well as to the possibilities they raise to help ease the pain in the world.