An emergency campaign has begun to try to immunise more than 15 million children in west and central Africa in just three days against a new threat of polio. Hundreds of thousands of health workers and volunteers are aiming to treat all children in Benin, Burkina Faso, Ghana, Niger and Togo following a fresh outbreak in neighbouring Nigeria. Nearly half of all polio cases in the world are in Nigeria – virtually all of them in the north of the country – and the aim of the current campaign is to halt the spread of the virus across Nigeria’s borders. Full Story