Microsoft founder Bill Gates and his wife Melinda have spoken to the BBC's James Robbins about their hopes for beating poverty and malnutrition and improving childhood health.

"We have to stay vigilant and the governments will act on these things the voters care about,'' said Mr Gates.

''Over time they're a reflection of the values of the people in the country - do they want to help out the poor, and are they making sure they've got a government that works on these issues? So it won't be easy.''