The United Nations said Tuesday a decade of intensive health campaign has cut new malaria infection rates by half and deaths by 38 per cent in 43 countries worst hit by the disease. "Malaria is on the retreat across the globe," UN Secretary General Ban Ki-moon said, as organizations involved in the fight reviewed their efforts at meetings in New York. Eleven African countries were among those where new infection cases dropped by half. Others countries that saw big drops were in Asia and Latin America. About 5 billion dollars had been spent in the past decade to fight malaria, with programmes like the distribution of hundreds of millions of insecticide-injected bed nets that repel mosquitoes known for causing malaria. The UN said about half of the world population, about 3.5 billion, had once been at risk of malaria, a preventable and treatable disease. Malaria killed an estimated 800,000 people worldwide in 2009.