WHO said some 1.5 billion people across 149 countries are affected by the diseases, insisting additional investments would save lives, prevent disability, end suffering and improve productivity.

"Increased investments by national governments can alleviate human misery, distribute economic gains more evenly and free masses of people long trapped in poverty," WHO Director General Margaret Chan said.

Dirk Engels, who heads the WHO department of control of neglected tropical diseases, told reporters in Geneva that Africa is the "continent where the most absolute number of these diseases occur," with many people suffering from more than one of them.

He said some 450 million people in sub-Saharan Africa are at risk of contracting these diseases.

But the diseases also hit people across Latin America, the Middle East, Central Asia and Asia, and can even appear in European countries, Japan and the United States, the WHO said.

In addition to dengue, sleeping sickness and leprosy, there are rabies, trachoma, buruli ulcer, yaws, chagas, leishmaniases, taeniasis, Guinea-worm disease, echinococcosis, foodborne trematodiases, lymphatic filariasis, river blindness, schistosomiasis, and soil-transmitted helminthiases.

The WHO recommends countries invest USD 2.9 billion (2.5 billion) annually until 2020 to treat the diseases or fight the insects and other vectors that carry them.

After that, it said, investment requirements for the subsequent decade would drop to USD 1.6 billion annually as the diseases are reduced or eliminated.

The total investment for 16 years adds up to USD 34 billion.

Great strides have already been made in some places, WHO officials said, pointing to the elimination of river blindness in Colombia in 2013.

Bangladesh and Nepal are meanwhile on a path to beating visceral leishmaniasis, a disease transmitted through the bites of infected female sandflies, and which attacks the internal organs.

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