JOHANNESBURG » Diarrhea kills 1.5 million young children a year in developing countries—more than AIDS, malaria and measles combined—but only four in 10 of those who need the oral rehydration solution that can prevent death for pennies get it.

“;All the attention has gone to more glamorous diseases, but this basic thing has been left behind,”; said Mickey Chopra, chief of health at UNICEF, which is trying to put diarrhea back on the global health agenda. “;It's a forgotten disease.”;

His observation lies at the heart of a wider debate over whether the United States and other rich nations spend too much on AIDS, which requires lifelong medications, compared with diarrhea and the other leading killer of children, pneumonia, both of which can be treated inexpensively.

The debate is flaring at a time of great opportunity and risk. Recent data has documented remarkable progress in reducing child mortality and treating people with AIDS. Foreign assistance, which has often delivered disappointing results, is helping save millions of lives, the new figures show.

But as the United States and other rich nations hit by the global financial crisis face their own daunting challenges, there is heightened competition for foreign assistance. President Barack Obama has proposed a 2 percent increase in HIV/AIDS spending for 2010 and a 6 percent rise for maternal and child health, according to the Global Health Council, but the disparity in American spending on AIDS and the big child killers remains stark.

In Africa's two most populous nations, Nigeria and Ethiopia, the number of people who died of AIDS in 2007—237,000—was less than half the 540,000 children under 5 who died of pneumonia and diarrhea. But this year, the $750 million the United States is spending on HIV/AIDS in the two countries not only dwarfs the $35 million it is spending there on maternal and child health, but is also more than the $646 million it is spending on maternal and child health in all the world's countries combined.

“;AIDS is still underfunded, no question,”; said Jeremy Shiffman, a political scientist at Syracuse University who has documented global health spending patterns. “;But maternal, newborn and child mortality is a tremendous tragedy and gets peanuts.”;

Dr. Ezekiel J. Emanuel—a bioethicist, White House official and brother of Rahm Emanuel, Obama's chief of staff—has contended that international aid for health is limited and would save more lives if increases focused on maternal health and the “;mundane but deadly diseases”; that kill young children. Such choices are necessary, he and a co-author wrote in the Journal of the American Medical Association in April, “;if the United States is going to shoulder the burden of choosing which lives to save in the developing world.”;

Jeffrey D. Sachs, the Columbia University economist, countered that wealthy donors still spent far too little on global health and rejected what he called the wrong-headed idea that “;we need to make a terrible and tragic choice between AIDS or pneumonia.”; The United States has invested heavily in the fight against AIDS, and other wealthy nations should pick up more of the cost of other global health priorities, he said. “;Rather than tearing down what's working, we should continue to invest in what's needed,”; he said.

Obama has promised to put greater focus on child and maternal health and proposed a 53 percent increase next year in money to fight malaria, a major killer of African children, the Global Health Council estimated. But he has also committed to major increases in money to fight AIDS in coming years that, if enacted, would ensure AIDS remained America's global health priority, constituting over 70 percent of its global health spending, he said.

International commitments to combat HIV and AIDS rose at an average annual rate of 48 percent from 1998 to 2007, reaching $7.4 billion and making up almost half of donor financing for global health, according to Professor Shiffman's analysis of data from the Organization for Economic Cooperation and Development.

Still, more than half the people with the disease who need drug treatment still are not getting it. Two million died in 2007, according to the Joint United Nations Program on HIV/AIDS.

The toll of women and children who die of easily preventable or curable conditions is even higher. Pneumonia alone killed two million children under age 5, and diarrhea 1.5 million more, out of the almost nine million young children who died last year.

Dr. Olivier Fontaine, who described himself as the only person at WHO working full time on childhood diarrheal diseases, said health ministry managers in poor countries know diarrhea is a crucial cause of child mortality, but focus on other diseases that have gotten more attention and financing from abroad.

Two days after her month-old son's bout of diarrhea began, Marcia Mankense, 23, took him to a hospital here in Johannesburg where a doctor administered fluids through an intravenous line threaded into his scalp.

Before his birth, she said, no one told her she should give him oral rehydration salts—known as ORS—as soon as he got diarrhea, though she was counseled on the need to get tested for HIV. Nor did anyone give her a packet of the salts to take home.

“;He's my firstborn and I know nothing about kids,”; she said, exhausted next to his crib after days of vigil. “;I just feel like I need to be here for him. What if he's crying?”;

Public health experts agree there is tremendous potential to lower child deaths from diarrhea and pneumonia substantially. New methods of distributing rehydration salts and cheap zinc tablets, also recommended for diarrhea, are being tested, including giving them away during national campaigns to hand out antimalarial bed nets and to vaccinate children against measles.

“;Everyone should have ORS at home like we have Band-aids,”; Fontaine said.

For an extra $3 billion to $4 billion in coming years, children in poor countries could be inoculated against pneumonia and the rotavirus that causes about a third of diarrhea deaths, according to the GAVI Alliance, a broad group of donors.

On the diarrhea ward at the hospital in Johannesburg, most of the babies and young children had mothers patiently sitting next to their cribs, comforting them. But one little boy, 2 months old, was alone. His mother, a 10th grader, was at school. He had come in dehydrated, with sunken eyes, too enervated to even cry. But after being given fluids intravenously, life flowed back into him.

When he howled, a nurse or one of the mothers would look into his eyes. He would fall quiet, his cries muting to soft mewling, his eyes widening curiously.

“;He wasn't even crying when he got here,”; Mankense said happily. “;Now we can hear his voice. He's naughty!”;