DAVOS, Switzerland (AP) -- Bill and Melinda Gates said Friday they were encouraging government and business leaders to keep investing in health and development in poor countries -- especially during the global financial crisis.

The founder of Microsoft Corp. and his wife said they came to the World Economic Forum in the Swiss Alps resort of Davos with the goal of keeping up the effort to improve the lot of the world's poorest people.

"We need to make sure that people in the U.S. or in the U.K. and the European countries understand that the aid money they are giving is working, and we need to keep up those levels," Melinda Gates said during an interview the couple gave to The Associated Press at the forum. "Aid is actually working."

She said a key goal is to get out the message that "during these economic times the people that get hit the hardest are the poor."

Initiatives to fight AIDS and other lethal diseases are saving millions of lives in the developing world, Mrs. Gates said.

Malaria infection rates have dropped in Zambia, Zanzibar, Ethiopia and elsewhere in Africa as a result of the distribution of bed nets that keep mosquitoes from biting people sleeping under them, she said.

"That has been very effective and has helped those malaria rates come down," Mrs. Gates said. "So we need to look beyond this crisis and say, 'OK, during this time keep up the aid money because we really are making an impact on those who are affected.'"

The couple announced Friday that the foundation is giving a $34 million grant to a network fighting diseases that afflict the world's poor.

Gates, the co-founder of Microsoft, said this year's meeting was the first time he had come to Davos to work exclusively on concerns of the foundation. He stepped down as CEO in 2000 and remains the software giant's chairman.

He said he now is working full-time at the foundation and finds it as enjoyable as the job he loved at Microsoft.

He said that after Davos he would go to northern Nigeria to promote continued growth in the use of polio vaccine as a crucial step in eradicating the disease after having made a similar trip recently to India, the other country hardest hit by polio.

New vaccines were saving millions of lives, and the foundation is employing scientists in the search for more, he said.

"In some cases where we tend to be the most unique is funding the creation of new vaccines and new drugs, and those things take a lot of time. We have had some very good successes. Two new vaccines are being given broadly to kids around the world."

He said he had just been in Brussels to visit the vaccine group that has been progressing in making malaria vaccine at GlaxoSmithKline PLC.

"The scientific work has gone well," Gates said. "That's always a high-risk business. We've had a few drug candidates that have not worked but that's why in the key diseases -- malaria, tuberculosis and AIDS -- we always have a lot of leads that we're working on. So that even if five out of six go away we'll still have a few that can provide the breakthrough."

He said he was hoping that researchers would come up with six new vaccineswhich might be enough to cut the number of childhood deaths in half by 2015.

Earlier this week Gates said the foundation would increase the share of assets it is giving away even though their value fell 20 percent last year.

But he noted the great benefit from fellow multibillionaire Warren Buffett's announcement in 2006 that he would give some $31 billion to the foundation, effectively doubling its assets.

"Warren Buffett's money coming to the foundation was an incredible thing," Gates said.

It advanced work on helping farmers in poor countries and on providing financial services for the poor, he said.

"We just feel so blessed that we've got Warren not only giving but also as a trustee so we've got his advice and his help," Gates said.

"No, nothing like that is going to come," he said. "We'll just make sure to take his resources and ours and use them in the best way possible."