A year and a half since an earthquake destroyed the Haitian capital Port-au-Prince, it is estimated at least 600,000 people still live in settlement camps, many facing a daily struggle for survival.Their story is one which Dr Paul Farmer - a US anthropologist and physician - tells in his new book Haiti: After the Earthquake.For three decades Dr Farmer has worked to help the people of the island nation. In this interview with the BBC’s Jane O'Brien, he says a cholera epidemic is still raging in Haiti, while most of the quake rubble has not been removed.