We've all heard a great deal by now about the diseases ravaging Africa: AIDS/HIV, tuberculosis, malaria. They are killing people by the millions and destroying families and communities across large parts of the continent. And while most of us would like to do something to help, the problem seems so huge, the prospective cost of dealing with it so immense, that one cannot even put a number on it.

Well, actually, one can put a number on it: about $8 a year from every one of us in America--roughly the cost of going out to a movie.

Let us see how this number is arrived at. A reasonable estimate is that sub-Saharan Africa will need at least $1 billion per year from donors--in addition to cancellation of the international debt that drains many treasuries--in order to cut sharply the burden of malaria on the continent. A typical assumption is that the United States should bear about 20 percent of any global effort, so the $1 billion from all sources would require about $200 million per year from this country--75 cents per American per year to save millions of lives from malaria.

Now add in the additional costs for greatly increased efforts to control AIDS, TB and the like. Even with the indirect expenses to the United States of debt cancellation, the sums are still quite small. For example, the United Nations recently estimated that around $4 billion per year is the amount needed worldwide to fight the HIV/ AIDS epidemic. A few billion dollars more could mount a similarly effective effort against tuberculosis and other deadly infectious diseases.

So suppose the world's rich countries came up with $10 billion per year to fight all these killer diseases--what would it cost us in America? Our $2 billion share of the contribution would require about $8 from every one of us.

And of course in the future, these costs could actually go down, not up--if vaccines can be developed for the diseases. President Clinton, with bipartisan support of Sens. Helms, Frist, Kerry, Roth and others, has wisely called for a new tax incentive scheme to encourage pharmaceutical firms to invest more heavily in research and development of vaccines for malaria, TB and HIV/AIDS.

Africa's present crisis has multiple and interconnected parts: the 500 million clinical cases and more than 1 million deaths per year from malaria; the HIV/AIDS epidemic, which now kills 2 million Africans per year; the tuberculosis crisis, re-surging on the back of AIDS, and claiming more than a million African lives per year, and interconnected crises of measles, diarrheal disease and undernourishment, claiming millions more. Life expectancy on the continent is around 50 years and falling.

Africa's disease burden not only causes untold human pain and suffering; it also cripples economic development. Malaria alone costs billions of dollars per year just in lost earnings and medical charges. The cost is many times that when we consider the longer- term effects of the disease such as suppressing foreign investment and educational attainment in the region.

Meanwhile, debt cancellation for Africa has come down to a matter of life and death. African leaders know very well that for their own countries to muster the internal resources to fight these dread diseases, they will have to be permitted by the creditor nations to shift the funds now spent on debt servicing into public health. The increased domestic resources would help get public health centers operating. The additional contributions from donor nations would be needed to procure vitally needed supplies such as insecticides, bed nets, anti-malarial medicines and the greatly expanded services of experts in fields such as entomology, immunology, parasitology and water resource management.

I will ask the question bluntly: Would Americans invest an extra 75 cents per year to battle malaria? Would they be ready to provide $8 per year as part of a global campaign to control and turn back a wider range of killer diseases, thereby saving millions of lives in sub-Saharan Africa?

In the America I know, the answer is surely yes--whether you are a liberal Democrat or a conservative Republican, a well-paid professional or a working-class family. All of us want to know that we have contributed to the good of humanity and to the lives of children everywhere. If given the opportunity, Americans would never allow it to pass.

The writer is the director of the Center for International Development at Harvard University.