Accra - Ending the deadliest Ebola outbreak in history is a difficult task, but it is "within our reach", the UN's new mission chief on the disease said, warning that the world has no choice but to beat back the infection."This is a global crisis. We definitely have a difficult time ahead of us, but we can achieve it," Ismail Ould Cheikh Ahmed, the new head of the UN Mission for Ebola Emergency Response (UNMEER), said on arrival in Ghana on Saturday."We have no plan B, we have to get rid of this virus. This is within our reach, but we should not be complacent," said Ahmed, a Mauritanian, who had arrived in Accra to officially assume duty, taking over from American Anthony Banbury.UNMEER, based in the Ghanaian capital, is leading international efforts in the battle against Ebola.'No other choice'According to the latest World Health Organization figures, there are more than 20 200 confirmed, probable or suspected cases of Ebola and just over 7 900 reported deaths. The three worst-affected countries are Sierra Leone, Liberia and Guinea."We need to keep going until we don't have even one case, because even one case is too many," he said. "The work ahead remains very hard but we really have no other choice," the Ebola mission chief added, according to the statement.Ahmed will be visiting Liberia and Sierra Leone this week, and Guinea shortly after, "to reinforce UNMEER's strategic priorities and see first-hand the Ebola response." the text said.He will be accompanied by UN Special Envoy on Ebola, David Nabarro, it added.