LONDON (Reuters) - Donating billions of dollars to global funds that fight poverty and disease is one of the best investments governments can make to boost security and economic growth, philanthropists Bill and Melinda Gates said on Thursday.

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Ending epidemics of infectious diseases such as malaria, polio, HIV and malaria is proving tough, they said, but dramatic progress made by global aid mechanisms recent decades means the world’s people are now healthier and more productive.

“The data has been really striking,” Melinda Gates told reporters on a teleconference.

She cited figures from the World Health Organization and others showing that since 1990, under-five mortality rates have fallen by more than 50 percent, and deaths due to infectious diseases like HIV, malaria and measles have also halved.

“A child born today is half as likely to die before the age of five, compared to if she was born in 2000,” Melinda Gates said. “The human and economic benefits of this are enormous.”

The multi-billion dollar philanthropic Gates Foundation she co-chairs with her husband Bill, the co-founder of Microsoft, is one of the largest funders of global health program aimed at helping poor people escape disease, poverty and premature death.

The Foundation is seeking to encourage international donor governments such as the United States, Japan, Australia, Germany, Britain and many others to replenish four key global funds in the next 18 months so they can continue their work.

The funds include the Global Fund to Fight AIDS, Tuberculosis and Malaria, the Global Polio Eradication Initiative (GPEI) and the GAVI vaccines alliance and the Global Financing Facility for child and maternal health.

Bill Gates said he was optimistic that wealthy donor governments remain committed to funding international aid for poor countries, but added: “We never want to take it for granted, because ... just one (donor) country dropping back could cost hundreds of thousands of lives.”

He also said he was concerned that “distraction by domestic issues” may mean the still urgent need for global aid funding may not get the attention it deserves.

“People shouldn’t become complacent,” he said. “We still have a little less than six million children who die under the age of five.”