It's hard not to cheer wildly. The Gates Foundation has given $4.2 billion to global health initiatives over the past 9 1/2 years, and you'd be hard-pressed to find any global health effort based in the United States that isn't getting Gates' money directly or via a secondary agency. (Full disclosure: The foundation partially funds the Global Health Program, which I run at the Council on Foreign Relations.)

But although Gates' money sets the agenda for a great deal of public health policy, it's important to remember what it isn't doing and won't do — the job of the WHO and the World Health Assembly.

The Gates Foundation, which has to answer only to its board, is adamant about its decision to primarily fund the search for cures and new treatments, rather than broader efforts to fight disease. It's a controversial position. An article in the British medical journal, the Lancet, recently took Gates to task, suggesting that trying to combat malaria, for instance, without also addressing problems like hygiene and water delivery could backfire.

In contrast to the agile, focused — but unaccountable — Gates Foundation, the WHO is governed by its often-embattled member states and lumbers along at a snail's pace, burdened by an obvious lack of clarity about its mission.

The problem isn't money, although more would help. The core budget of the WHO is just $400 million, but it doesn't operate on that sum alone. More than 70 percent of its budget comes from wealthy-nation donors supporting specific programs, which brings real spending to about $1.5 billion a year. (Still not a big number; it's roughly the same as the annual budget of the New York City Department of Health.)

But because the WHO is so reliant on that wealthy-donor "soft money," its mission is swayed — in too many directions — by those countries' agendas, ideologies and pet projects. In a world of globalized health threats, this is nuts. The WHO has to be able to put its resources where its experts can empirically show they are most needed.

Last week alone, there were 16 disease outbreaks in 13 countries, including deadly Ebola and Marburg viruses, polio, meningitis and, most ominous of all, avian flu. Scientists fear that it could mutate and cause a contagious killer pandemic.

Yet right now, the entire global alert and response operation for epidemics at the WHO is — brace yourself — five people, out of roughly 6,000 employees.

The Gates Foundation isn't going to deploy emergency response teams around the world, send scientists in spacesuits wading into Marburg outbreaks or lead a global response to pandemic flu. That's the WHO's job.

The delegates to the World Health Assembly have the power to remake the WHO. Instead of shifting personnel and funds from Geneva headquarters to regional offices, the WHO should establish a smart, mobile global health force, based in Geneva, that can respond to crises around the world. Wealthy nations should be urged — shamed — into funding it, for the sake of their own survival.

And instead of beefing up mini-WHO bureaucracies around the world, the agency should fix public health systems in poor countries — training personnel, funding labs and communication systems so that local healthcare workers can respond to new disease outbreaks.

Bill and Melinda Gates deserve a global standing ovation. But the delegates at the World Health Assembly cannot afford to be even temporarily blinded by Gates' star power and generosity. Could they hear what he said as they cheered?

"The world is failing billions of people," he warned. "There is no bigger test for humanity than the crisis of global health."