Mortality rates in a refugee camp in South Sudan are nearly double the threshold for an emergency, Medecins Sans Frontieres has warned.This means that about eight children are dying every day in the camp, which houses 40,000 people from the conflict in Sudan's Blue Nile state.The medical charity said people were dying of preventable diseases because of "horrific living conditions".Latrines have overflowed, contaminating water sources, because of heavy rains.Jamam camp is one of three refugee camps in South Sudan's Upper Nile state where about 120,000 people have fled.MSF is calling for urgent action by the UN refugee agency, which says it has been trying to move people from unsuitable locations but the pace of new arrivals and shortfall in funding and resources has compounded the challenge.South Sudan seceded from Sudan exactly a year ago next Monday - as part of a deal to end years of civil war.Since then conflicts have erupted in two of Sudan's border states where communities traditionally allied to the south found themselves north of the border after Juba's independence.